# Undeliverable mail: forwarding, endorsements and ACS

USPS forwards, returns or discards mail that is undeliverable as addressed, depending on its mail class, the mailer's endorsement and any change-of-address order.[^1][^2] The mailer finds out from the returned piece, a printed notice such as PS Form 3547, or an electronic notice from the [Address Change Service](https://postalref.com/products/address-change-service.md).[^3][^4]

Updated November 5, 2026. 82 sources.

## Questions

### What does Return Service Requested mean on a piece of mail?

Return Service Requested is an [ancillary service endorsement](https://postalref.com/products/ancillary-service-endorsement.md) asking USPS to return an undeliverable piece with the new address or reason for nondelivery attached.[^5] USPS does not forward the piece, even when the addressee has filed a change-of-address order.[^5][^6] First-Class Mail comes back at no charge, while a USPS Marketing Mail mailer pays a single-piece price for each returned piece.[^5][^7]

### What does Change Service Requested mean on an envelope?

Change Service Requested asks USPS to discard an undeliverable piece and send the mailer a notice of the new address or reason for nondelivery.[^5] First-Class Mail may carry it only with the electronic [Address Change Service](https://postalref.com/products/address-change-service.md).[^5] Its second option forwards the piece during the first 12 months of a change-of-address order instead.[^8]

### What does Forwarding Service Requested mean on an envelope?

Forwarding Service Requested asks USPS to forward a piece to the addressee's new address where forwarding is not normally provided.[^5] It asks for no address correction, so it does not meet the [Move Update](https://postalref.com/products/move-update.md) standard.[^5] On USPS Marketing Mail, the mailer generally pays the [weighted fee](https://postalref.com/products/ancillary-service-endorsement.md), a single-piece price times 2.472, on every piece that comes back.[^7]

### Can presorted First-Class Mail be forwarded or returned to sender?

Yes, the default for undeliverable First-Class Mail is to forward it or return it to the sender.[^3] With no [ancillary service endorsement](https://postalref.com/products/ancillary-service-endorsement.md), USPS forwards the piece at no charge during months 1 through 12 of a change-of-address order.[^7] Without an order on file, the piece comes back with the reason for nondelivery attached, also at no charge.[^7]

### Can USPS Parcel Select be forwarded to another address?

Yes, USPS forwards Parcel Select as postage due to the addressee during the first 12 months of a change-of-address order.[^7] It goes only to domestic addresses, and the addressee may refuse it.[^7] [Shipper Paid Services](https://postalref.com/products/shipper-paid-services.md) lets the shipper pay the forwarding postage instead, which makes a refusal less likely.[^9]

### Why is my mail being returned as undeliverable as addressed?

USPS returns mail it can't deliver as addressed when its mail class allows, and marks each piece with the reason, such as an incomplete, illegible or incorrect address.[^7] Mail at a correct address is undeliverable too when the addressee is unknown there, has moved or died, refuses it, or leaves it unclaimed.[^7] The [Address Change Service](https://postalref.com/products/address-change-service.md) reports such reasons to mailers electronically, such as Attempted Not Known.[^10] A correct-looking address can still come back after a USPS adjustment, such as renumbered houses or a renamed street.[^7] A carrier may also have delivered a wrongly addressed piece for years, knowing where it goes; a new carrier without that knowledge marks it undeliverable, such as No Such Number or No Such Street.[^11]

### What happens if USPS cannot deliver a package?

USPS forwards an undeliverable package, returns it to the sender or discards it, depending on its mail class, the sender's [endorsement](https://postalref.com/products/ancillary-service-endorsement.md) and any change-of-address order.[^2] A package that can be neither delivered nor returned goes to the local Post Office or the USPS Mail Recovery Center.[^12] Contents worth more than $25.00 are held for 60 days when the package is barcoded, or 30 days when it is not.[^12]

### What does USPS Address Service Requested mean?

Address Service Requested asks USPS to forward the piece when possible and send the mailer a separate notice of the new address, for a fee.[^13] A piece that cannot be forwarded comes back with the reason it could not be delivered.[^13] USPS does not recommend it for USPS Marketing Mail, whose returned pieces pay the [weighted fee](https://postalref.com/products/ancillary-service-endorsement.md).[^13]

## How it fits together

USPS forwards mail that is undeliverable as addressed, returns it to the sender, or treats it as dead mail, as each mail class allows.[^7] Forwarding needs a change-of-address order from the addressee.[^1] By default, USPS Marketing Mail is disposed of instead.[^3] [Secure Destruction](https://postalref.com/products/secure-destruction.md), an opt-in service, shreds undeliverable First-Class Mail letters and flats that hold personal information instead of returning them.[^14] A business can also have all its mail forwarded for a time through [Premium Forwarding Service Commercial](https://postalref.com/products/premium-forwarding-services-commercial.md).[^15]

A mailer asks for other treatment with an [ancillary service endorsement](https://postalref.com/products/ancillary-service-endorsement.md) printed on the piece.[^16] The endorsement can also ask for a notice of the new address or the reason for nondelivery.[^7] Without electronic service, that notice is a PS Form 3547 or the returned piece itself.[^17] Endorsements and the Address Change Service are the post-mailing methods of [Move Update](https://postalref.com/guides/move-update.md), the USPS standard for matching mailers' address records with change-of-address orders.[^18][^19]

The [Address Change Service](https://postalref.com/products/address-change-service.md), or ACS, sends these notices electronically, and it has four kinds.[^4][^20]

- [Traditional ACS](https://postalref.com/products/traditional-acs.md) reads a Participant ID printed in the address block.[^21]
- [OneCode ACS](https://postalref.com/products/onecode-acs.md) reads the Intelligent Mail barcode on letters and flats.[^22]
- Full-Service ACS is OneCode ACS for [Full-Service](https://postalref.com/guides/full-service.md) mail, which pairs a unique barcode on every piece, tray and container with electronic documentation.[^23][^24]
- [IMpb ACS](https://postalref.com/products/intelligent-mail-package-barcode-impb-acs.md) reads the Intelligent Mail package barcode on parcels.[^25]

SingleSource ACS combines all of a mailer's notices into one file.[^4]

What forwarding and return cost depends on the mail class.[^26] [Shipper Paid Services](https://postalref.com/products/shipper-paid-services.md) lets a parcel shipper pay forwarding or return postage through its ACS account instead of the customer.[^27]

## Forwarding, return and disposal

Post Offices keep a record of permanent change-of-address orders for 18 months.[^7] Forwarding generally lasts for the first 12 of those months.[^7] A temporary order forwards mail for no more than 12 months.[^7] USPS does not forward mail addressed to a commercial mail receiving agency.[^7]

What USPS does with an undeliverable piece by default depends on its [mail class](https://postalref.com/guides/mail-classes.md).[^26]

| Mail class | Default treatment |
| --- | --- |
| First-Class Mail | Forwarded, or returned to the sender[^3] |
| Periodicals | Forwarded free for 60 days, then discarded with a PS Form 3579 sent to the publisher[^7][^28] |
| USPS Marketing Mail and Bound Printed Matter | Disposed of[^3] |
| Parcel Select | Forwarded postage due during months 1 through 12, to domestic addresses only[^7] |

USPS marks each piece it can't deliver as addressed with one of its own endorsements, each naming a reason for nondelivery, such as these.[^7]

| USPS endorsement | Reason for nondelivery |
| --- | --- |
| `Attempted—Not Known` | Delivery was attempted, and the addressee is not known at the address[^7] |
| `Deceased` | The addressee is known to have died, and no one else can properly receive the mail; the delivery employee must mark it personally, never with a rubber stamp[^7] |
| `Illegible` | The address can't be read[^7] |
| `Insufficient Address` | The address lacks a number, street, box number, route number or section of the city, or omits the city and state, and the correct address is not known[^7] |
| `Moved, Left No Address` | The addressee moved and filed no change-of-address order[^7] |
| `No Such Number` | The number does not exist, and the correct number is not known[^7] |
| `No Such Street` | The street does not exist, and the correct street is not known[^7] |
| `Not Deliverable as Addressed—Unable to Forward` | The mail can't be delivered at the address, and no change-of-address order is on file or the forwarding order expired[^7] |
| `Refused` | The addressee refused to accept the mail or to pay postage charges on it[^7] |
| `Returned for Postage` | The mail has no postage, or shows that its postage fell off[^7] |
| `Unclaimed` | The addressee abandoned the mail or failed to call for it[^7] |
| `Vacant` | The building is not occupied; used only on mail addressed to "Occupant"[^7] |

Mail with no specific address and no sender instructions is held 5 days on a rural or highway contract route.[^7] General delivery lets customers with proper identification pick up mail at a Post Office.[^29] Its mail is held 10 days at an office with city carriers and 15 days at one without.[^7] Deliverable mail for a Post Office box goes back only after the box is declared vacant, except mail such as Certified Mail.[^7]

Certified Mail, Registered Mail and other signed-for mail goes back to the sender 15 days after a delivery notice if no one calls for it.[^30] Priority Mail Express goes back after 5 days and COD after 10, unless the sender prints fewer days on the piece.[^30] On other mail, a sender can ask for a hold of 3 to 30 days by printing it in the return address.[^7]

Undeliverable letters and flats that automation can process go through the Postal Automated Redirection System, which has three modes.[^31] Its Intercept mode catches a letter sent to the old address on a change-of-address order and checks that the names match.[^31] A matched letter goes to a Combined Input Output Sub-System, a [mail processing](https://postalref.com/guides/mail-processing.md) machine that prints a label to redirect it.[^31] Its Return to Sender mode handles mail that is undeliverable for reasons other than a change of address.[^31] The Computerized Forwarding System makes ACS data and manual notices for parcels and for letters and flats that automation can't process.[^31]

Dead mail is mail that USPS can neither deliver nor return to the sender.[^7] Mail recovery centers open dead letters to find an address for delivery or return.[^7]

Green & Secure is the set of ACS options that a Change Service Requested Service Type ID, a code in the piece's barcode, asks for.[^32] It lets USPS dispose of undeliverable pieces with or without secure destruction.[^32] It covers First-Class Mail and USPS Marketing Mail letters and flats, but only First-Class Mail can use secure destruction.[^32] [Secure Destruction](https://postalref.com/products/secure-destruction.md) shreds those pieces, and mailers pay no extra fee to take part.[^31][^33]

[Premium Forwarding Service Commercial](https://postalref.com/products/premium-forwarding-services-commercial.md) forwards all of a business's mail for a time to its domestic address, by Priority Mail Express or Priority Mail.[^15] The business pays an annual enrollment fee and postage for each shipment.[^15] As of July 12, 2026, the online enrollment fee is $26.40 a year.[^34] The mail ships in containers that pay Priority Mail Express or Priority Mail postage, or in flat rate tray boxes where USPS has them.[^34]

| Flat rate tray box, July 12, 2026 | Priority Mail | Priority Mail Express |
| --- | --- | --- |
| Half tray box | $33.15[^34] | $76.00[^34] |
| Full tray box | $60.55[^34] | $150.60[^34] |

- **return to sender**, also called RTS, returned to the sender, returned to sender: “A general designation for undeliverable-as-addressed mail that cannot be forwarded because no active change-of-address order is on file or because the sender has endorsed the mail “Return Service Requested” and an active change-of-address order is on file.”[^6]
- **Carrier Identified Forward**, also called CIF, Carrier ID Forward, PARS CARRIER IDENTIFIED: “the processing mode for automation-compatible flats and letters that were not intercepted and were sorted to the delivery unit”[^31]
- **Flats Postal Automated Redirection Software**, also called FPARS, Flats PARS: “First class flat mail is processed using Flats Postal Automated Redirection Software (FPARS) on an Automated Flats Sorting Machine (AFSM100).”[^35]
- **dead mail**: “Mail that is undeliverable as addressed or undeliverable at a forwarding address and cannot be returned to the sender (usually because there is no return address on the piece or the classification of the mail does not entitle it to return service).”[^36]
- **mail recovery center**, also called MRC, dead letter office, dead parcel branch: “A postal facility designated only to receive and attempt to return undeliverable and unforwardable mail of obvious value. Unpaid mail without a return address is also sent to the mail recovery center. The mail recovery center is located in Atlanta. Formerly called dead letter office, dead letter branch, or dead parcel branch.”[^37]

## Ancillary service endorsements

An ancillary service endorsement is printed on the piece, and USPS reads it when the piece is undeliverable as addressed.[^16] The endorsements are the same for every mail class, but the treatment and cost differ by class.[^26] Using one means the mailer agrees to pay any fees the services add.[^16]

With ACS, the endorsements have disposition options that manual address correction lacks.[^38] Each option has its own [Service Type ID](https://postalref.com/products/stids.md), a code the mailer puts in the Intelligent Mail barcode.[^38]

Service Type IDs that ask for each endorsement option on First-Class Mail letters and flats.[^38]

| STID | Group | Option | Service level | Informed Visibility Mail Tracking & Reporting |
| --- | --- | --- | --- | --- |
| `230` | OneCode ACS® | Address Service Requested Opt 1 | Basic or Nonautomation | Without IV® MTR |
| `220` | OneCode ACS® | Address Service Requested Opt 1 | Basic or Nonautomation | With IV® MTR |
| `080` | OneCode ACS® | Address Service Requested Opt 2 | Basic or Nonautomation | Without IV® MTR |
| `140` | OneCode ACS® | Address Service Requested Opt 2 | Basic or Nonautomation | With IV® MTR |
| `504` | OneCode ACS® | Change Service Requested Opt 1 ♻ | Basic or Nonautomation | Without IV® MTR |
| `502` | OneCode ACS® | Change Service Requested Opt 1 ♻ | Basic or Nonautomation | With IV® MTR |
| `082` | OneCode ACS® | Change Service Requested Opt 2 ♻ | Basic or Nonautomation | Without IV® MTR |
| `240` | OneCode ACS® | Change Service Requested Opt 2 ♻ | Basic or Nonautomation | With IV® MTR |
| `341` | OneCode ACS® | Return Service Requested Opt 2 | Basic or Nonautomation | Without IV® MTR |
| `340` | OneCode ACS® | Return Service Requested Opt 2 | Basic or Nonautomation | With IV® MTR |
| `345` | OneCode ACS® | Temp-Return Service Requested Opt 2 | Basic or Nonautomation | Without IV® MTR |
| `344` | OneCode ACS® | Temp-Return Service Requested Opt 2 | Basic or Nonautomation | With IV® MTR |

12 codes in the Service Type IDentifier (STID) Table, effective January 21, 2024, where Table is First-Class Mail® and Group is OneCode ACS®.

Electronic Service Requested only points to the actual service, which the barcode or the mailer's ACS profile names.[^39] When the barcode's Service Type ID and the printed endorsement disagree, the printed endorsement takes precedence.[^40]

> The words “Option 1” or “Option 2” must not be part of the “Address Service Requested” or “Change Service Requested” endorsement on mailpieces.[^7]

**Must.** A mailer must not add the option number to a printed Address Service Requested or Change Service Requested endorsement.[^7]

- **Forwarding Service Requested**, also called FSR: “this endorsement does not request address corrections. It is used only to request forwarding where forwarding service is not normally provided.”[^5]
- **Temp-Return Service Requested**, also called TRSR: “This endorsement is similar to Return Service Requested, however if the change-ofaddress is temporary, the piece will be forwarded to the temporary address.”[^5]
- **Address Service Requested Option 1**, also called ASR1: “Mailpiece forwarded during months 1 through 12; separate electronic notice of new address provided. After month12 or if undeliverable for other reason, mailpiece returned with new address or reason for non-delivery attached.”[^8]
- **Address Service Requested Option 2**, also called ASR2, Option 2 (ASR2): “Same as Option 1, ACS notice provided for returned mailpiece.”[^32]
- **Change Service Requested Option 1**, also called CSR1: “Separate notice of new address or reason for nondelivery provided; mailpiece disposed of by USPS (recycled).”[^8]
- **Change Service Requested Option 2**, also called CSR2, Option 2 (CSR2): “Same as Option 1, but mail will be forwarded for a change-of-address during months 1 through 12.”[^8]
- **RSR1**: “OPTION 1 (RSR1) accessed only with the printed endorsement. No ACS notices generated.”[^41]
- **Return Service Requested Option 2**, also called RSR2: “OPTION 2 (RSR2) accessed by using the appropriate STID. ACS notices generated.”[^41]
- **TRSR1**: “OPTION 1 (TRSR1) accessed only with the printed endorsement. No ACS notices generated.”[^42]
- **Temp - Return Service Requested Option 2**, also called TRSR2: “OPTION 2 (TRSR2) accessed by using the appropriate STID. ACS notices generated.”[^42]

## Address correction notices

Without ACS, the notice is a printed form or the returned piece.[^17] PS Form 3547 shows an image of the piece with the new address or the reason it was not delivered.[^17] For Periodicals, PS Form 3579 gives the address and the correction or reason, and goes to the publisher named in the postage statement.[^17] Manual notices are often the most costly and least effective way to keep a list current.[^3]

ACS reports two situations: the addressee filed a change of address, or the piece is undeliverable for another reason.[^10] Notices of the second kind, called Nixies, come from what the delivery employee knows about the addressee and the address.[^43] A change-of-address notice gives a foreign new address when USPS knows it.[^44][^45]

USPS charges no fee to sign up for ACS, but charges for each record.[^46] Electronic notices cost much less than manual ones.[^13] Full-Service ACS is free for qualifying [Full-Service](https://postalref.com/guides/full-service.md) mail, though forwarding fees still apply.[^47][^48] When mail properly prepared for ACS gets a manual notice instead, the mailer is entitled to pay the electronic fee.[^49] The mailer must ask its local Post Office for a refund of the difference.[^49]

SingleSource ACS invoices come from the National Customer Support Center in Memphis.[^50][^51] Each must be paid, with a copy of its remittance slip, within 30 days of the invoice date.[^52] As of October 18, 2019, they could be paid by credit card or ACH credit, an overnight bank-to-bank transfer.[^52][^53] The center's Accounts Receivable Department, at 901-681-4658, gave the details.[^52] Customers of the Electronic Payment System could instead email acs@usps.gov to have their ACS account set up for it.[^52]

USPS licenses neither the [Intelligent Mail barcode](https://postalref.com/products/intelligent-mail-barcode.md) nor ACS, and it recommends no service provider.[^44] USPS recommends testing the barcode before mailing by sending at least 20 sample pieces for review.[^54] The samples should carry different names and addresses, not one piece printed again and again.[^44] For Full-Service ACS, each piece's barcode must be unique for 45 days from the postage statement mailing date.[^55][^56]

OneCode, Traditional and SingleSource ACS notices arrive through [Electronic Product Fulfillment](https://postalref.com/guides/address-matching.md), the secure USPS website that also posts USPS address products.[^44][^57] Full-Service ACS notices arrive as COA and Nixie reports in the [Business Customer Gateway](https://postalref.com/guides/business-accounts.md).[^58] SingleSource ACS is open to all mailers who want every notice in one file from one source.[^51]

An existing Traditional ACS or OneCode ACS account can become a SingleSource account.[^59] The mailer completes the ACS Enrollment Form with its existing ACS account number, shown on its ACS invoices as the `MEM` number.[^59] A Traditional ACS account needs a [Mailer ID](https://postalref.com/products/mid.md), the 6- or 9-digit number that identifies a mailer, added before it can change.[^59][^60] A mailer that already uses Electronic Product Fulfillment needs no new access request on PS Form 5116 unless it wants another login.[^56]

- **PS Form 3579**: “PS Form 3579 for periodicals consists of the mailpiece address and the address correction or reason for nondelivery.”[^17]
- **ACS COA and Nixie Reports**, also called Full-Service ACS Documentation: “Full-Service ACS is made available through the ACS COA and Nixie Reports in the Business Customer Gateway.”[^58]
- **Full-Service ACS Change-of-Address (COA) Report**, also called COA detail online report: “Mailers presenting Full-Service mailings are provided an online Change-of-Address downloadable report and automated data exchange.”[^48]
- **Full-Service ACS Nixie Report**, also called Nixie Feedback, nixie detail online report: “Mailers presenting Full-Service mailings are provided an online Nixie downloadable report and automated data exchange.”[^48]
- **Full Service ACS Qualified**, also called FSA: Full Service ACS Qualified (FSA) is the ACS type an ACS product code marks with 36, its first two digits.[^61] An ACS product code is a six-digit number assigned to an ACS type, mail class, notice type and shape.[^47] Each ACS notice carries its product codes, which can be matched to the ACS shipping notice and the ACS invoice.[^62] FSA marks the Full-Service ACS notices of full-service mailpieces that qualified, which USPS provides at no charge.[^47] A notice provided free that later fails to qualify is charged under a Full Service Chargeback code instead.[^47] FSA notices come in the ACS fulfillment file when the ACS account is a SingleSource ACS account.[^63] (Explained by a model. USPS doesn’t define it.)
- **Full Service Chargeback**: “reflects charges for previously fulfilled Full Service ACS notices that were provided free and subsequently did not qualify for Full Service.”[^47]
- **Full-Service Chargeback Report**, also called Full Service Chargeback ACS Report and Data files, Full-Service Chargeback ACS data, Full Service Chargeback data files: “The chargeback report is a data file that is used only when it is later determined that a Full-Service ACS notice previously provided at no charge did not qualify for the discounts and benefits of full-service mail.”[^64]
- **Residual ACS**, also called Residual: “Residual is part of the Address Quality Census Measurement and Assessment Process and provides ACS notifications at no charge based on the Mailer Scorecard.”[^65]
- **OneCode ACS account**: “All OneCode ACSTM notices may be fulfilled to this account, as well as the SD Notification file. Only ACSTM from undeliverable mail with a Basic IMbTM will be provided”[^66]
- **SingleSource ACS account**: “All Full Service ACSTM, OneCode ACSTM, and Traditional ACSTM notices may be fulfilled to this account, as well as the SD Notification file”[^66]

## Paying for forwarding and return

First-Class Mail postage covers basic forwarding and return, but not address correction fees.[^67] USPS Marketing Mail postage covers neither forwarding nor return.[^67] The weighted fee applies when USPS Marketing Mail or nonprofit mail carries an endorsement that asks for forwarding.[^68] A Marketing Mail piece endorsed Return Service Requested pays a single-piece price for its weight and shape when it comes back.[^7]

Forwarded Package Services parcels arrive postage due at the new address.[^9] If the addressee refuses to pay, the parcel goes back and the mailer pays both forwarding and return postage.[^9] [Shipper Paid Services](https://postalref.com/products/shipper-paid-services.md) lets the shipper pay forwarding postage through its ACS account, so a refusal is less likely.[^9] Its Shipper Paid Return option lets the shipper pay return postage for undeliverable parcels through the same account.[^69]

For IMpb ACS, USPS takes a forwarded or returned parcel's weight and mail class from the detail record of its [Shipping Services File](https://postalref.com/guides/package-payment.md), version 1.7 or higher.[^70] That file holds the package's manifest and payment information.[^60] A package with scan events but no manifest is unmanifested.[^71] As of January 6, 2026, [USPS Ship](https://postalref.com/products/usps-ship.md) flags an undeliverable package returned past 120 days as unmanifested.[^72][^73] As of that date, USPS was working on requirements to detect such returns and turn off the fees for unmanifested packages.[^72][^73]

[Bulk Parcel Return Service](https://postalref.com/products/bulk-parcel-return-service.md), one of USPS's return services, brings large quantities of undeliverable USPS Marketing Mail machinable parcels back to designated postal facilities.[^74] The mailer pays only a per-piece fee for each parcel returned, not postage, and the service's permit carries no annual fee.[^74]

- **Forwarding and/or Return Postage and Fees**: “any additional charges that are applied to the product or service, such as postage for shipper paid services such as Shipper Paid Forwarding, Shipper Paid Return, and Additional Service Fees applied to undeliverable Parcel Select mail.”[^75]
- **mailer-paid forwarding ACS option**: “for Marketing Mail letters and flats that will charge the forwarding postage to the mailer and does not require the non-forwardable mail to be returned at the weighted fee”[^28]
- **IMpb ACS with SPS**: “an ACS option that provides a consistent and more efficient method of collecting forwarding and return charges for undeliverable as addressed (UAA) parcels”[^76]
- **Shipper Paid Services option**: “allows for the forwarding of the parcel when a change of address is available, but the parcels will not be returned if undeliverable for reasons other than a move.”[^69]
- **IMpb ACS with Shipper Paid Forwarding**: “provides an option for the shipper to pay the forwarding postage via the ACS account, minimizing the chance that the parcel will be refused.”[^69]
- **Traditional ACS SPF**: “is an ACS fulfillment option that allows parcel mailers to receive and electronic address correction and pay forwarding postage via their ACS account”[^77]
- **Weighted Fee**: “the appropriate single-piece First-Class Mail or Priority Mail price, plus the non-machinable surcharge when applicable, multiplied by 2.472 and rounded to the next whole cent”[^67]

## What goes wrong

- An [ancillary service endorsement](https://postalref.com/products/ancillary-service-endorsement.md) needs a return address on the face of the piece.[^78]
- USPS does not accept mail that bears invalid or conflicting endorsements.[^7]
- Printing Electronic Service Requested on mail that does not ask for [ACS](https://postalref.com/products/address-change-service.md) adds work, and the mailer will likely pay the cost.[^28]
- ACS is not guaranteed, so some manual notices still arrive.[^79]
- When an addressee refuses a postage-due parcel, the mailer pays both forwarding and return postage, which [Shipper Paid Services](https://postalref.com/products/shipper-paid-services.md) makes less likely.[^9]
- An unendorsed Parcel Select package that comes back pays return postage at the USPS Ground Advantage Commercial price plus the additional service fee.[^7]
- A parcel with a registered Mailer ID but no printed endorsement gets no [IMpb ACS](https://postalref.com/products/intelligent-mail-package-barcode-impb-acs.md) notice.[^80]
- Pieces that institutions such as hospitals and universities return as undeliverable produce no ACS records.[^81]
- [Full-Service ACS](https://postalref.com/products/address-change-service.md) notices that cannot be matched to the mailing's electronic documentation are charged in the next billing cycle.[^50]
- USPS gives no refund for duplicate [OneCode ACS](https://postalref.com/products/onecode-acs.md) notices from several pieces mailed to the same addressee.[^82]

## Index: 71 entries

### Services (35)

- [Address Change Service](https://postalref.com/products/address-change-service.md)
- [Address Service Requested](https://postalref.com/products/shipper-paid-services.md#terms)
- [Address Service Requested Option 1](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [Address Service Requested Option 2](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [Ancillary Service Endorsement](https://postalref.com/products/ancillary-service-endorsement.md)
- [Change Service Requested](https://postalref.com/products/shipper-paid-services.md#terms)
- [Change Service Requested Option 1](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [Change Service Requested Option 2](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [Change-of-Address](https://postalref.com/products/traditional-acs.md#terms)
- [Electronic Service Requested](https://postalref.com/products/onecode-acs.md#terms)
- [Forwarding Service Requested](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [Full-Service ACS](https://postalref.com/products/address-change-service.md#terms)
- [Green & Secure](https://postalref.com/products/secure-destruction.md#terms)
- [IMpb ACS with Shipper Paid Forwarding](https://postalref.com/guides/undeliverable-mail.md#paying)
- [IMpb ACS with SPS](https://postalref.com/guides/undeliverable-mail.md#paying)
- [Intelligent Mail Package Barcode (IMpb) ACS](https://postalref.com/products/intelligent-mail-package-barcode-impb-acs.md)
- [mailer-paid forwarding ACS option](https://postalref.com/guides/undeliverable-mail.md#paying)
- [OneCode ACS](https://postalref.com/products/onecode-acs.md)
- [Premium Forwarding Service](https://postalref.com/products/premium-forwarding-services-commercial.md#terms)
- [Premium Forwarding Service Commercial](https://postalref.com/products/premium-forwarding-services-commercial.md)
- [Residual ACS](https://postalref.com/guides/undeliverable-mail.md#notices)
- [Return Service Requested](https://postalref.com/products/ancillary-service-endorsement.md#terms)
- [Return Service Requested Option 2](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [RSR1](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [Secure Destruction](https://postalref.com/products/secure-destruction.md)
- [Shipper Paid Forwarding](https://postalref.com/products/traditional-acs.md#terms)
- [Shipper Paid Return](https://postalref.com/?q=Shipper%20Paid%20Return)
- [Shipper Paid Services](https://postalref.com/products/shipper-paid-services.md)
- [Shipper Paid Services option](https://postalref.com/guides/undeliverable-mail.md#paying)
- [SingleSource ACS](https://postalref.com/products/address-change-service.md#singlesource-acs)
- [Temp - Return Service Requested Option 2](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [Temp-Return Service Requested](https://postalref.com/guides/undeliverable-mail.md#endorsements)
- [Traditional ACS](https://postalref.com/products/traditional-acs.md)
- [Traditional ACS SPF](https://postalref.com/guides/undeliverable-mail.md#paying)
- [TRSR1](https://postalref.com/guides/undeliverable-mail.md#endorsements)

### Systems (2)

- [Flats Postal Automated Redirection Software](https://postalref.com/guides/undeliverable-mail.md#forwarding)
- [Postal Automated Redirection System](https://postalref.com/products/address-change-service.md#terms)

### Files (7)

- [ACS COA and Nixie Reports](https://postalref.com/guides/undeliverable-mail.md#notices)
- [ACS Shipping Notice](https://postalref.com/?q=ACS%20Shipping%20Notice)
- [Full-Service ACS Change-of-Address (COA) Report](https://postalref.com/guides/undeliverable-mail.md#notices)
- [Full-Service ACS Nixie Report](https://postalref.com/guides/undeliverable-mail.md#notices)
- [Full-Service Chargeback Report](https://postalref.com/guides/undeliverable-mail.md#notices)
- [Nixie Notice](https://postalref.com/products/address-change-service.md#terms)
- [Secure Destruction Notification](https://postalref.com/products/secure-destruction.md#terms)

### Identifiers (2)

- [Keyline](https://postalref.com/products/address-change-service.md#terms)
- [Participant ID](https://postalref.com/products/address-change-service.md#terms)

### Documents (2)

- [PS Form 3547](https://postalref.com/products/ancillary-service-endorsement.md#terms)
- [Publication 8](https://postalref.com/?q=Publication%208)

### Facility (1)

- [Computerized Forwarding System](https://postalref.com/products/address-change-service.md#terms)

### Role (1)

- [Business Associate](https://postalref.com/products/secure-destruction.md#terms)

### Terms (21)

- [ACS Profile](https://postalref.com/products/intelligent-mail-package-barcode-impb-acs.md#terms)
- [Attempted—Not Known](https://postalref.com/?q=Attempted%E2%80%94Not%20Known)
- [Carrier Identified Forward](https://postalref.com/guides/undeliverable-mail.md#forwarding)
- [Combined ACSTM account](https://postalref.com/?q=Combined%20ACSTM%20account)
- [Forwarding and/or Return Postage and Fees](https://postalref.com/guides/undeliverable-mail.md#paying)
- [FSB](https://postalref.com/?q=FSB)
- [FSD](https://postalref.com/?q=FSD)
- [FSF](https://postalref.com/?q=FSF)
- [FSU](https://postalref.com/?q=FSU)
- [Full Service ACS Qualified](https://postalref.com/guides/undeliverable-mail.md#notices)
- [Full Service Chargeback](https://postalref.com/guides/undeliverable-mail.md#notices)
- [Insufficient Address](https://postalref.com/?q=Insufficient%20Address)
- [Nixies](https://postalref.com/products/secure-destruction.md#terms)
- [No Such Number](https://postalref.com/?q=No%20Such%20Number)
- [OneCode ACS account](https://postalref.com/guides/undeliverable-mail.md#notices)
- [P-Level 1](https://postalref.com/?q=P-Level%201)
- [P-Level 4](https://postalref.com/products/secure-destruction.md#terms)
- [return to sender](https://postalref.com/guides/undeliverable-mail.md#forwarding)
- [SingleSource ACS account](https://postalref.com/guides/undeliverable-mail.md#notices)
- [Undeliverable as Addressed](https://postalref.com/products/address-change-service.md#terms)
- [Weighted Fee](https://postalref.com/guides/undeliverable-mail.md#paying)

## Sources

[^1]: [OneCode ACS® Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/OneCodeACSTechnicalGuide.pdf#page=11), page 11: “The mail class (First-Class Mail®, Periodical, USPS Marketing Mail™, or Bound Printed Matter), the mailer’s requested ancillary service, and the age or existence of a COA determines whether the mailpiece is forwarded, discarded, or returned to sender. … The USPS® can forward mail or notify mailers of a Change of Address (COA) only if the customer submits a change of address request with the Postal Service™.”

[^2]: [Intelligent Mail® Package Barcode (IMpb) ACS™ Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2024-02/IMpb_ACS_Technical_Guide.pdf#page=10), page 10: “The mail class (USPS Ground Advantage, Periodical, USPS Marketing Mail™, or Package Services/Parcel Select), the mailer’s requested ACS ancillary service, and the age or existence of a COA determines whether the parcel is forwarded, discarded, or returned to sender.”

[^3]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=31), page 28: “When an Ancillary Service Endorsement is used, the process of notifying a mailer that a mailpiece was UAA is done via a hardcopy notice (PS Form 3547) or by returning the mailpiece with the notice information on the piece. … For First-Class Mail, the default treatment for mailpieces that cannot be delivered as addressed is either for the mailpiece to be forwarded or to be returned to the sender. … For USPS Marketing Mail and Bound Printed Matter, the default treatment of UAA mail is to dispose of it. … However, because stand-alone Ancillary Service Endorsements require manual operations, they are often the most costly and least effective way to maintain address lists for customer change-of-address.”

[^4]: [PostalPro: ACS™](https://postalpro.usps.com/address-quality/ACS): “ACS is a post mailing service that allows mailers to receive change-of-address (COA) and other reasons for non-delivery electronically and reduce the number of manual (hardcopy) address notifications. … With SingleSource ACS, all of the ACS notices are combined into a single file format and are provided via Electronic Product Fulfillment (EPF).”

[^5]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=8), page 5: “Return Service Requested: The mailpiece is returned with the new address information or reason for nondelivery affixed. … No forwarding service is provided. … The return of First-Class Mail is provided at no charge. … Change Service Requested: A separate notice of new address or reason for nondelivery is provided and the manual address correction fee is charged. … The Postal Service disposes of the mailpiece. … This endorsement is not available for First-Class Mail unless used in conjunction with electronic ACS. … It is used only to request forwarding where forwarding service is not normally provided. … That is because this endorsement does not request address corrections. … Note that Forwarding Service Requested is not listed as a move update compliant ancillary service endorsement. … this endorsement does not request address corrections. It is used only to request forwarding where forwarding service is not normally provided. … This endorsement is similar to Return Service Requested, however if the change-ofaddress is temporary, the piece will be forwarded to the temporary address.”

[^6]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=197), page 193: “A general designation for undeliverable-asaddressed mail that cannot be forwarded because no active change-of-address order is on file or because the sender has endorsed the mail “Return Service Requested” and an active change-of-address order is on file. … A general designation for undeliverable-as-addressed mail that cannot be forwarded because no active change-of-address order is on file or because the sender has endorsed the mail “Return Service Requested” and an active change-of-address order is on file.”

[^7]: [DMM 507: Mailer Services](https://pe.usps.com/text/dmm300/507.htm): “The mailer of a returned piece endorsed “Return Service Requested” is charged the applicable single-piece First-Class Mail or USPS Ground Advantage – Retail price for the weight and shape of the piece, and the nonmachinable surcharge if applicable. … When forwarding service is provided, generally the mailer of USPS Marketing Mail is subject to paying additional postage: the USPS Marketing Mail weighted fee on all returns. … The weighted (per piece) fee is the First-Class Mail, USP Ground Advantage — Retail, or Priority Mail single-piece price and any nonmachinable surcharge … multiplied by 2.472, rounding any fractions to the next whole cent. … Same treatment as “Forwarding Service Requested.” … Months 1 through 12: Piece forwarded (no charge). … Piece returned with reason for nondelivery attached (no charge). … Months 1 through 12: Package Services forwarded postage due at the single-piece price for the class of mail. … Parcel Select forwarded as postage due to addressee at the Ground Advantage – Commercial price plus the additional service fee. … Package Services and Parcel Select mail is forwarded only to domestic addresses. … The addressee may refuse any piece of Package Services or Parcel Select that has been forwarded. … Mail that is undeliverable as addressed is forwarded, returned to the sender, or treated as dead mail, as authorized for the particular class of mail. … Undeliverable-as-addressed mail is endorsed by the USPS with the reason for nondelivery … Incomplete, illegible, or incorrect address. … Addressee not at address (unknown, moved, or deceased). … Mail refused by the addressee at time of delivery. … Mail unclaimed. … Mail can be undeliverable because of USPS adjustments such as the following: … a. Renumbering of houses. … b. Renaming of streets. … A mailer endorsement is used to request forwarding, return, or address correction service. … A record of permanent change-of-address orders is kept by Post Offices for 18 months, from the end of the month when the change takes effect. … Generally, forwarding is available for the first 12 months. … A customer temporarily moving away may have mail forwarded for a specific period of time, not to exceed 12 months (364 total consecutive days). … Mail addressed to an addressee at a commercial mail receiving agency (CMRA) is not forwarded through the USPS. … Periodicals publications (including publications pending Periodicals authorization) are forwarded without charge for 60 days when postage is fully prepaid by the sender. … | Attempted—Not Known | Delivery attempted; addressee not known at place of address. | … Used only when known that addressee is deceased, and mail is not properly deliverable to another person. … This endorsement must be made personally by delivery employee and under no circumstance may it be rubber-stamped. … Address not readable. … Mail without number, street, box number, route number, or geographical section of city or city and state omitted, and correct address not known. … | Moved, Left No Address | Addressee moved and filed no change-of-address order. | … Addressed to nonexistent number and correct number not known. … Addressed to nonexistent street and correct street not known. … | Not Deliverable as Addressed— Unable to Forward | Mail undeliverable at address given; no change-of-address order on file; forwarding order expired. | … Addressee refused to accept mail or pay postage charges on it. … | Returned for Postage | Mail without postage or indication that postage fell off. | … Addressee abandoned or failed to call for mail. … House, apartment, office, or building not occupied. (Use only if mail addressed “Occupant.”) … Mail without a specific address or instructions from the sender is held: … For 5 days if for delivery by rural or highway contract route carrier. … For 10 days if for general delivery at an office with city carrier service. … For 15 days if for general delivery at an office without city carrier service. … Deliverable mail addressed to a Post Office box is not returned until after the box is declared vacant, except for certified, collect on delivery (COD), insured, registered, postage due, Adult Signature and perishable mail. … At the sender’s request, the delivery Post Office holds mail, other than Registered Mail, Insured, Certified Mail, COD, Adult Signature, and Signature Confirmation, for no fewer than 3 days or more than 30 days. … A specific retention time of not less than 3 or more than 30 days, if requested, must be included by the sender in the return address on the mailpiece (e.g., “Return in 30 days to” followed by sender’s return address). … Dead mail is matter deposited in the mail that is undeliverable and cannot be returned to the sender. … Dead letters are opened at mail recovery centers to determine the name and address of the addressee or sender to permit delivery or return. … The words “Option 1” or “Option 2” must not be part of the “Address Service Requested” or “Change Service Requested” endorsement on mailpieces. … Material bearing invalid or conflicting ancillary service endorsements will not be accepted for mailing. … Piece returned with reason for nondelivery attached; return postage charged at the applicable Package Services single-piece price or the USPS Ground Advantage – Commercial price plus the additional service fee.”

[^8]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=44), page 41: “Same as Option 1, but mail will be forwarded for a change-of-address during months 1 through 12. … Mailpiece forwarded during months 1 through 12; separate electronic notice of new address provided. After month12 or if undeliverable for other reason, mailpiece returned with new address or reason for non-delivery attached. … Separate notice of new address or reason for nondelivery provided; mailpiece disposed of by USPS (recycled).”

[^9]: [Traditional ACS™ with Shipper Paid Services Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2024-01/Trad_ACS_Shipper_Paid_Svs_Tech_Guide.pdf#page=7), page 7: “Shipper Paid Service provides an option for the shipper to pay the forwarding postage via the ACS account, minimizing the chance that the parcel will be refused. … Package Services parcels and Bound Printed Mail flats that must be forwarded will arrive as “Postage Due” at the new address. … If the addressee refuses the piece to avoid paying the forwarding postage, the parcel is returned to the mailer, and both the forwarding and return postage is charged.”

[^10]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=39), page 39: “ACS provides electronic notification for two different types of Undeliverable-as-Addressed (UAA) mail situations; either there is a COA on file, or the mail is determined to be UAA for a reason other than a move (i.e. Attempted Not Known, No Such Number, Unable To Forward/Forwarding Time Expired).”

[^11]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=29), page 29: “For example, Letter Carrier A has the knowledge to complete the delivery of a particular mail piece that has an incorrect primary number or street name and could have been doing so for years. … Carrier A retires, goes on vacation, or changes routes. Carrier B takes over and does not have the same knowledge. … New Carrier B determines this mail to be UAA and identifies it as a Nixie because there is No Such Number or No Such Street.”

[^12]: [Ancillary Services for Parcel Select and Parcel Select Lightweight FAQs](https://postalpro.usps.com/mnt/glusterfs/2022-07/Ancillary%20Services%20Parcel%20Select%20and%20Parcel%20Select%20Lightweight%20FAQs%20(002).pdf#page=2), PDF page 2: “Undeliverable mailpieces are letters, flats or parcels that cannot be delivered as addressed nor returned to the sender. … These mailpieces are either handled by the local Post Office™ or sent to the USPS® Mail Recovery Center (MRC). … Undeliverable mail determined to be of value, meaning the content is worth more than $25.00 ($20.00 for mailpieces containing cash), will be held for 60 days if the mailpiece is barcoded, or 30 days for non-barcoded mailpieces.”

[^13]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=7), page 4: “Address Service Requested: The mailpiece is forwarded to the new address when possible and a separate notice with the new address is sent to the mailer and the manual address correction fee is charged. … If mail cannot be forwarded, it is returned with the reason it cannot be delivered. … This endorsement is not recommended for USPS Marketing Mail because the Weighted Fee is charged for returned mail, which is equal to the comparable First-Class Mail postage, plus any non-machinable surcharges, multiplied by 2.472. … Electronic and automated address correction fees are significantly lower than the fees charged for manual (hard-copy) address correction notices.”

[^14]: [PostalPro: Secure Destruction](https://postalpro.usps.com/mailing/secure-destruction): “Part of the USPS® BlueEarth sustainability initiatives and an opt-in service, this new program securely shreds and recycles letter and flat-sized pieces of Undeliverable-As-Addressed (UAA) First-Class Mail® with personal protected information that would otherwise be returned to the sender (RTS).”

[^15]: [PostalPro: Premium Forwarding Service Commercial®](https://postalpro.usps.com/premium_forwarding_commercial): “Premium Forwarding Service Commercial™ (PFSC) allows business customers with an active P.O. Box or street address to temporarily forward all mail to their domestic address using Priority Mail Express® or Priority Mail®. … An annual enrollment fee is required, and applicable postage is charged for each shipment.”

[^16]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=32), page 29: “Ancillary Service Endorsements are printed on a mailpiece and recognized by the Postal Service when processing UAA mail. … The use of an Ancillary Service Endorsement represents the mailers’ acknowledgement of an agreement to pay any additional fees associated with these additional services.”

[^17]: [A Guide to Full Service](https://postalpro.usps.com/mnt/glusterfs/2018-03/AGuidetoFullService.pdf#page=20), page 14: “When an ASE is used without an ACS, either a hard copy address correction (PS Form 3547 or 3579) or the return of the piece fulfills the mailer's request. … PS Form 3547 provides an image of the First-Class, Standard, or package services mailpiece with either the recipient's new address or the reason the piece couldn’t be delivered. … PS Form 3579 for periodicals consists of the mailpiece address and the address correction or reason for nondelivery. … It is mailed to the publisher identified in the postage statement.”

[^18]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=17), page 14: “Of the primary methods, NCOALink including NCOALink MPE are known as “pre-mailing” methods; ACS and Ancillary Service Endorsements are known as “post mailing” methods.”

[^19]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=16), page 13: “The Move Update standard is a means of reducing the number of mailpieces in a mailing that require forwarding or return by the periodic matching of a mailer’s address records with change-of-address orders received and maintained by the Postal Service.”

[^20]: [OneCode ACS® Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/OneCodeACSTechnicalGuide.pdf#page=7), page 7: “ACS has four distinct implementation methods OneCode ACS, Full Service ACS, IMpb ACS and Traditional ACS.”

[^21]: [Traditional ACS™ Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2019-10/TraditionalACSTechnicalGuide.pdf#page=8), page 8: “Participation in Traditional ACS requires the mailer to include the USPS assigned Participant ID and optional keyline in the address block on the mailpiece (see Exhibit 1).”

[^22]: [OneCode ACS® Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/OneCodeACSTechnicalGuide.pdf#page=8), page 8: “OneCode ACS allows customers mailing First-Class Mail®, USPS Marketing Mail™, and Periodical flats or letters to receive electronic or automated address corrections using the Intelligent Mail® barcode.”

[^23]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=4), page 4: “Full-Service ACS is OneCode ACS for Full-Service mail”

[^24]: [Publication 685: Publication for Streamlined Mail Acceptance for Letters and Flats](https://about.usps.com/publications/pub685.pdf#page=15), PDF page 15: “Full-Service combines the use of unique barcodes on each container, tray and mailpiece with electronic submission of postage statements and documentation.”

[^25]: [PostalPro: Intelligent Mail® Package Barcode (IMpb) ACS™](https://postalpro.usps.com/mailing-and-shipping-services/IMpb-ACS): “IMpb ACS allows parcel mailers who print the Intelligent Mail package barcode to receive an electronic address correction using that barcode.”

[^26]: [Ancillary Services for Parcel Select and Parcel Select Lightweight FAQs](https://postalpro.usps.com/mnt/glusterfs/2022-07/Ancillary%20Services%20Parcel%20Select%20and%20Parcel%20Select%20Lightweight%20FAQs%20(002).pdf#page=1), PDF page 1: “The endorsements are the same for all classes of mail, but the treatment and cost differ by class of mail.”

[^27]: [PostalPro: Shipper Paid Services](https://postalpro.usps.com/shipping/shipper-paid-services): “Shipper Paid Services is an ACS fulfillment option that allows parcel mailers to receive an electronic address correction and pay forwarding or return postage via their ACS account rather than charging the customer.”

[^28]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=9), page 9: “After 60 days and for all non-forwardable mail, the USPS discards the mail and sends Form 3579 address correction notice to the address indicated in the ID statement of the publication. … for Marketing Mail letters and flats that will charge the forwarding postage to the mailer and does not require the non-forwardable mail to be returned at the weighted fee … If Electronic Service Requested is printed on mail that does not request ACS, it will cause unnecessary and costly additional workload for the Postal Service, and you will likely have to pay any postage or fees that are charged as a result of its improper use.”

[^29]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=97), page 93: “An alternate delivery service that allows customers with proper identification to pick up mail at Post Offices.”

[^30]: [DMM 508: Recipient Services](https://pe.usps.com/text/dmm300/508.htm): “The following conditions also apply to the delivery of Priority Mail Express, Registered Mail, Certified Mail, mail insured for more than $500.00, Adult Signature, or COD, as well as mail for which a return receipt is requested or the sender has specified restricted delivery. … If the piece is not called for or redelivery is not requested, the piece is returned to the sender after 15 days (5 days for Priority Mail Express, 10 days for COD), unless the sender specifies fewer days on the piece.”

[^31]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=30), page 30: “There are 3 PARS modes of operation: Intercept (INT) – is available only for automation compatible letters. … PARS for Automation Letters and Flats will provide four possible results: … Letter automation has the ability to capture letter mail that is addressed to the OLD address of a COA, validate that the name on the mail matches the name on the COA, and redirect it without having to go to the carrier of the old address first. … If a match is confirmed, the mail piece is directed to a PARS CIOSS (Combined Input Output Sub-System) that has image capture and character reading capability and has been retrofitted with a label applicator and printer so the mail can be redirected as needed. … Return to Sender (RTS) – is the processing mode used for automation-compatible letter and flat mail that is undeliverable for reasons other than a COA. … For OneCode ACS, Full-Service ACS, Traditional ACS, and IMpb ACS, CFS will generate ACS data and manual address correction notices for parcels and non-automation compatible letters and flats that cannot be processed by PARS or CFS. … A First-Class Mail piece is sorted for Secure Destruction and the mail piece is shredded. … the processing mode for automation-compatible flats and letters that were not intercepted and were sorted to the delivery unit”

[^32]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=45), page 42: “Mailpieces bearing an ACS Change Service Requested Service Type ID is considered a Green & Secure option. … Green & Secure allows USPS to dispose of undeliverable mailpieces in one of two ways, either with or without secure destruction. … It is available for First-Class Mail and USPS Marketing Mail letters and flats, however only First-Class Mail can utilize the secure destruction option. … Same as Option 1, ACS notice provided for returned mailpiece.”

[^33]: [Secure Destruction Frequently Asked Questions (FAQs)](https://postalpro.usps.com/mnt/glusterfs/2025-05/SD%20FAQS%20Ver%202%20May%2019%202025.pdf#page=1), PDF page 1: “There are no additional fees for mailer participation in this service.”

[^34]: [PRC: Mail Classification Schedule through July 12, 2026 (docx, converted to HTML with mammoth)](https://www.prc.gov/sites/default/files/mcs/MCS%20Through%2007122026.docx): “(Revisions Through July 12, 2026) … | Online Enrollment (Commercial, ~~and~~ Residential, and Local) | 26.40 | … Customers must pay the Online Enrollment fee annually. … Containers are used based on volumes and are charged the appropriate Priority Mail Express or Priority Mail postage. … Flat rate tray boxes may be used, when available. … | Priority Mail Half Tray Box (Commercial Only) | 33.15 | … | Priority Mail Express Half Tray Box (Commercial Only) | 76.00 | … | Priority Mail Full Tray Box (Commercial Only) | 60.55 | … | Priority Mail Express Full Tray Box (Commercial Only) | 150.60 |”

[^35]: [Secure Destruction Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2025-03/SD%20eNotification%20Guide%20Ver%2012.pdf#page=6), page 6: “First class flat mail is processed using Flats Postal Automated Redirection Software (FPARS) on an Automated Flats Sorting Machine (AFSM100).”

[^36]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=61), page 57: “Mail that is undeliverable as addressed or undeliverable at a forwarding address and cannot be returned to the sender (usually because there is no return address on the piece or the classification of the mail does not entitle it to return service).”

[^37]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=131), page 127: “A postal facility designated only to receive and attempt to return undeliverable and unforwardable mail of obvious value. Unpaid mail without a return address is also sent to the mail recovery center. The mail recovery center is located in Atlanta. Formerly called dead letter office, dead letter branch, or dead parcel branch.”

[^38]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=43), page 40: “ACS Ancillary Service Endorsements have additional mail disposition options that are not available with manual address corrections. … Each of the endorsements and options have Service Type IDs assigned to them that must be used in the IMb when these options are desired.”

[^39]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=55), page 52: “Electronic Service Requested must be used in conjunction with ACS/OneCode ACS/Full-Service ACS, but Electronic Service Requested just acts as a pointer to another actual service, such as Address Service Requested or Change Service Requested which exists in the Intelligent Mail barcode or in the mailer’s ACS profile.”

[^40]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=33), page 30: “If a conflict exists between the request represented by the Service Type ID in the IMb and the printed ancillary service endorsement, the printed endorsement will take precedence.”

[^41]: [OneCode ACS® Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/OneCodeACSTechnicalGuide.pdf#page=21), page 21: “OPTION 1 (RSR1) accessed only with the printed endorsement. No ACS notices generated. … OPTION 2 (RSR2) accessed by using the appropriate STID. ACS notices generated.”

[^42]: [OneCode ACS® Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/OneCodeACSTechnicalGuide.pdf#page=22), page 22: “OPTION 1 (TRSR1) accessed only with the printed endorsement. No ACS notices generated. … OPTION 2 (TRSR2) accessed by using the appropriate STID. ACS notices generated.”

[^43]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=8), page 8: “This is because ACS Nixies result from the delivery employee knowledge regarding the addressee and the address.”

[^44]: [Appendix B: ACS™ Frequently Asked Questions](https://postalpro.usps.com/mnt/glusterfs/2026-04/AppendixB_ACSFAQ.pdf#page=5), page 5: “Yes, if known. … The Postal Service does not license the Intelligent Mail® barcode or the ACS product. … There may be service providers that may be able to perform this function for you; however, the USPS cannot recommend any particular company. … The samples should reflect different names and addresses. Printing the same piece repeatedly does not reflect a real world scenario. … OneCode, Traditional & SingleSource ACS customers use the EPF website.”

[^45]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=28), page 28: “ACS can provide the foreign address, but NCOALink cannot because NCOALink provides only delivery point valid (DPV) addresses.”

[^46]: [Appendix B: ACS™ Frequently Asked Questions](https://postalpro.usps.com/mnt/glusterfs/2026-04/AppendixB_ACSFAQ.pdf#page=4), page 4: “There are no fees for signing up for ACS; however, there are fees for each record provided.”

[^47]: [Appendix C: ACS™ Product Code Information and Details](https://postalpro.usps.com/mnt/glusterfs/2024-12/AppendixC_ACSProductCodeInfoandDetails.pdf#page=5), page 4: “In addition to full-service postage discounts and benefits, FS ACS is provided at no charge for qualifying full-service mail pieces. … Product Code: a six-digit number that is assigned to a specific ACS type, mail class, ACS notice type, and mail processing category (shape). … Full Service Chargeback – reflects charges for previously fulfilled Full Service ACS notices that were provided free and subsequently did not qualify for Full Service. … reflects charges for previously fulfilled Full Service ACS notices that were provided free and subsequently did not qualify for Full Service.”

[^48]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=39), page 36: “Full-Service ACS is provided at no charge, but forwarding fees will be applied. … Mailers presenting Full-Service mailings are provided an online Change-of-Address downloadable report and automated data exchange. … Mailers presenting Full-Service mailings are provided an online Nixie downloadable report and automated data exchange.”

[^49]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=16), page 16: “Manual COA and Nixie notices provided on mail that was properly prepared to generate ACS, but a PS Form 3547 or 3579 was generated instead, are entitled to pay the Electronic address correction fees. … A refund for the difference in fees charged must be requested at your local Post Office.”

[^50]: [Appendix B: ACS™ Frequently Asked Questions](https://postalpro.usps.com/mnt/glusterfs/2026-04/AppendixB_ACSFAQ.pdf#page=9), page 9: “SingleSource ACS invoices come from the NCSC in Memphis, TN instead of going through Eagan, MN and San Mateo, CA. … Mailpieces with a Full Service STID that cannot be matched to an eDoc are considered “Unassociated” and are not provided in the Full Service COA and Nixie reports through the Business Customer Gateway. … The Unassociated IMb is reported to the mailer and charges are applied for the record in the next available billing cycle.”

[^51]: [SingleSource ACS™ Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/SingleSourceACSTechGuide.pdf#page=6), page 6: “The United States Postal Service® provides support for SingleSource ACS through the National Customer Support Center (NCSC) in Memphis TN. … While intended and designed primarily for Full Service qualified mailers, SingleSource ACS is available to ALL mailers that desire to receive all of their ACS notices in a single file format and from a single fulfillment source.”

[^52]: [SingleSource ACS™ Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/SingleSourceACSTechGuide.pdf#page=10), page 10: “Payment must be submitted with a copy of the invoice remittance slip within 30 days of the invoice date. … October 18, 2019 v 1.12 … Credit Card and ACH Credit payment options available to NCSC Accounting customers please contact the NCSC Accounts Receivable Department at 901-681-4658 for information. … Electronic Payment System (EPS) customers can email acs@usps.gov and request your ACS account to be setup for EPS.”

[^53]: [Enterprise Payment System (EPS) Deposit Instructions](https://postalpro.usps.com/mnt/glusterfs/2026-04/EPS%20Deposit%20Instructions%20April%202026.pdf#page=1), page 1: “ACH Credit is an overnight method of moving funds from one bank to another.”

[^54]: [OneCode ACS® Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/OneCodeACSTechnicalGuide.pdf#page=38), page 38: “The following procedures are voluntary and are not required for activation; however the Postal Service highly recommends that your Intelligent Mail barcode is tested prior to mailing. … Once a mailpiece has been finalized, create a minimum of 20 sample mailpieces that contain the Intelligent Mail Barcode.”

[^55]: [A Guide to Full Service](https://postalpro.usps.com/mnt/glusterfs/2018-03/AGuidetoFullService.pdf#page=8), page 2: “Ensure all containers, trays, and pieces have an Intelligent Mail Barcode that is unique for 45 days from the postage statement mailing date.”

[^56]: [Appendix B: ACS™ Frequently Asked Questions](https://postalpro.usps.com/mnt/glusterfs/2026-04/AppendixB_ACSFAQ.pdf#page=8), page 8: “The 45-day window starts on the day the piece was mailed in a Full Service mailing. … If you are already an OneCode or Traditional ACS customer, you are a current EPF user and you will not need to submit an additional Web Access Request Form (PS 5116), unless an additional EPF login is desired.”

[^57]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=43), page 43: “a secure web-based application managed by the National Customer Support Center in Memphis TN that is used to post and receive Address Management and Address Information System products, including ACS fulfillment files.”

[^58]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=19), page 19: “Full-Service ACS is made available through the ACS COA and Nixie Reports in the Business Customer Gateway.”

[^59]: [SingleSource ACS™ Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/SingleSourceACSTechGuide.pdf#page=13), page 13: “An existing Traditional ACS or OneCode ACS account may be changed to a SingleSource account or you may request a new SingleSource account. … To change an existing ACS account to a SingleSource account, complete the ACS Enrollment form and include your existing ACS account number in the fields provided. … If you do not know your existing ACS Account number, you can find it on the current ACS Invoices, identified as the “MEM” number. … Existing Traditional ACS accounts that are changed to a SingleSource account must have a MID added to the account before it can be changed.”

[^60]: [Publication 199: Intelligent Mail Package Barcode (IMpb) Implementation Guide for Confirmation Services and Electronic Payment Systems](https://postalpro.usps.com/mnt/glusterfs/2026-07/Pub%20199_v35_07022026.pdf#page=473), page 474: “MID is a unique 6- or 9-digit number that identifies the mailer or the mailer’s client. … The electronic file containing all manifest and payment information.”

[^61]: [Appendix C: ACS™ Product Code Information and Details](https://postalpro.usps.com/mnt/glusterfs/2024-12/AppendixC_ACSProductCodeInfoandDetails.pdf#page=7), page 6: “36 = FULL SERVICE ACS QUALIFIED (FSA) 1ST 2 CHARACTERS”

[^62]: [ACS™ File Format Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2019-10/ACSFileFormatTechnicalGuide.pdf#page=20), page 17: “The product code(s) in each ACS notice can be matched to the ACS Shipping Notice and the ACS Invoice.”

[^63]: [ACS™ File Format Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2019-10/ACSFileFormatTechnicalGuide.pdf#page=30), page 27: “Full Service ACS notices are included in the ACS fulfillment when the ACS account is identified as a SingleSource ACS fulfillment account.”

[^64]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=38), page 38: “The chargeback report is a data file that is used only when it is later determined that a Full-Service ACS notice previously provided at no charge did not qualify for the discounts and benefits of full-service mail.”

[^65]: [OneCode ACS® Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/OneCodeACSTechnicalGuide.pdf#page=12), page 12: “Residual is part of the Address Quality Census Measurement and Assessment Process and provides ACS notifications at no charge based on the Mailer Scorecard.”

[^66]: [Secure Destruction Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2025-03/SD%20eNotification%20Guide%20Ver%2012.pdf#page=7), page 7: “All OneCode ACSTM notices may be fulfilled to this account, as well as the SD Notification file. Only ACSTM from undeliverable mail with a Basic IMbTM will be provided … All Full Service ACSTM, OneCode ACSTM, and Traditional ACSTM notices may be fulfilled to this account, as well as the SD Notification file”

[^67]: [Ancillary Service Endorsement Fact Sheet](https://postalpro.usps.com/mnt/glusterfs/2026-03/Ancillary%20Service%20Endorsement%20Fact%20Sheet.pdf#page=1), PDF page 1: “First-Class Mail postage covers basic forwarding and return service but does not include Address Correction Service fees. … USPS Marketing Mail postage does not cover forwarding and return service. … the appropriate single-piece First-Class Mail or Priority Mail price, plus the non-machinable surcharge when applicable, multiplied by 2.472 and rounded to the next whole cent”

[^68]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=17), page 17: “The weighted fee is applied when Marketing Mail and Nonprofit mail is endorsed with an ancillary service that includes a request for forwarding.”

[^69]: [Intelligent Mail® Package Barcode (IMpb) ACS™ Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2024-02/IMpb_ACS_Technical_Guide.pdf#page=9), page 9: “Shipper Paid Forwarding / Return (SPF/R) service is an IMpb ACS fulfillment option that allows parcel shippers to receive an electronic address correction notice and pay forwarding or return postage for their undeliverable parcels via their ACS account. … They may also pay for any return postage via Shipper Paid Return services if desired. … allows for the forwarding of the parcel when a change of address is available, but the parcels will not be returned if undeliverable for reasons other than a move. … provides an option for the shipper to pay the forwarding postage via the ACS account, minimizing the chance that the parcel will be refused.”

[^70]: [Intelligent Mail® Package Barcode (IMpb) ACS™ Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2024-02/IMpb_ACS_Technical_Guide.pdf#page=12), page 12: “The weight and mail class of the parcel is determined by the detail record of the Shipping Services File (SSF - version 1.7 or higher). … The weight and mail class of the parcel provided in the detail record of the Shipping Services File (SSF) version 1.7 or higher).”

[^71]: [Publication 199: Intelligent Mail Package Barcode (IMpb) Implementation Guide for Confirmation Services and Electronic Payment Systems](https://postalpro.usps.com/mnt/glusterfs/2026-07/Pub%20199_v35_07022026.pdf#page=475), page 476: “Packages for which the USPS has scan events and no associated manifest are considered unmanifested.”

[^72]: [USPS Ship Frequently Asked Questions](https://postalpro.usps.com/mnt/glusterfs/2026-01/20260106_USPS_Ship_FAQs_0.pdf#page=1), page 1: “Updated January 6, 2026”

[^73]: [USPS Ship Frequently Asked Questions](https://postalpro.usps.com/mnt/glusterfs/2026-01/20260106_USPS_Ship_FAQs_0.pdf#page=6), page 6: “We are working on putting in specific requirements to detect those instances and turn off the unmanifested fees, because right now, when these packages are returned past 120 days they are flagged as unmanifested.”

[^74]: [DMM 505: Return Services (July 2026)](https://pe.usps.com/text/dmm300/505.htm): “Bulk parcel return service (BPRS) allows mailers of large quantities of USPS Marketing Mail machinable parcels that are undeliverable-as-addressed or un-opened and refused by addressees to be returned to designated Postal Service facilities. … Each piece returned through BPRS is charged only the per piece fee, not postage, regardless of weight. … A BPRS permit is required to participate in BPRS; no annual fee is required to obtain a BPRS permit.”

[^75]: [Appendix C: ACS™ Product Code Information and Details](https://postalpro.usps.com/mnt/glusterfs/2024-12/AppendixC_ACSProductCodeInfoandDetails.pdf#page=6), page 5: “any additional charges that are applied to the product or service, such as postage for shipper paid services such as Shipper Paid Forwarding, Shipper Paid Return, and Additional Service Fees applied to undeliverable Parcel Select mail.”

[^76]: [Publication 199: Intelligent Mail Package Barcode (IMpb) Implementation Guide for Confirmation Services and Electronic Payment Systems](https://postalpro.usps.com/mnt/glusterfs/2026-07/Pub%20199_v35_07022026.pdf#page=25), page 26: “an ACS option that provides a consistent and more efficient method of collecting forwarding and return charges for undeliverable as addressed (UAA) parcels”

[^77]: [Traditional ACS™ Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2019-10/TraditionalACSTechnicalGuide.pdf#page=31), page 31: “is an ACS fulfillment option that allows parcel mailers to receive and electronic address correction and pay forwarding postage via their ACS account”

[^78]: [PostalPro: Ancillary Service Endorsements](https://postalpro.usps.com/address-quality/ancillary-service-endorsements): “A return address is required on the face of the mailpiece when using ancillary service endorsements.”

[^79]: [Traditional ACS™ Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2019-10/TraditionalACSTechnicalGuide.pdf#page=10), page 10: “ACS is not a guaranteed service. Manual notices may still be received, although reduced in volume.”

[^80]: [Intelligent Mail® Package Barcode (IMpb) ACS™ Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2024-02/IMpb_ACS_Technical_Guide.pdf#page=16), page 16: “If the registered MID is used in the IMpb on a parcel of any mail class that has no printed ancillary endorsement, IMpb ACS will not be provided.”

[^81]: [Traditional ACS™ Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2019-10/TraditionalACSTechnicalGuide.pdf#page=13), page 13: “COA records from colleges and universities, individuals within a business, or other single-point deliveries including, but not limited to, commercial mail receiving agencies (CMRA), prisons, hospitals, nursing homes, campus dormitories, and sorority or fraternity houses are not accepted or processed by the USPS. … Pieces returned as undeliverable by these institutions are not eligible to produce ACS records.”

[^82]: [OneCode ACS® Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/OneCodeACSTechnicalGuide.pdf#page=14), page 14: “Refunds for duplicate ACS notices will not be provided for multiple ACS notices generated from multiple mail pieces that request ACS and are mailed to the same addressee.”

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