# Address matching: CASS, DPV and USPS address data

[CASS](https://postalref.com/products/coding-accuracy-support-system.md)-certified address-matching software standardizes an address and matches it to USPS's ZIP + 4 and City State Products to assign its ZIP + 4 and delivery point codes.[^1][^2] [DPV](https://postalref.com/products/delivery-point-validated.md) then confirms whether USPS delivers to the address, and LACSLink and SuiteLink supply converted addresses and missing suite numbers.[^3][^4][^5]

Updated November 5, 2026. 92 sources.

## Questions

### How do I know if USPS delivers to my address?

Delivery Point Validation, or DPV, is the USPS check in CASS-certified address-matching software that confirms whether USPS delivers to an address.[^3][^6] An address on a phantom route, where USPS provides no delivery, gets [DPV](https://postalref.com/products/delivery-point-validated.md)'s enhanced return code `R` and only a 5-digit ZIP Code.[^7][^8] DPV also flags vacant addresses, which were active in the past but no longer receive delivery.[^9] When someone creates a USPS.com account, usps.com checks the home address entered and says whether it is verified as a valid delivery address.[^10]

### Is my address in the USPS database?

Every address USPS delivers to is in the Address Management System, USPS's national database of delivery addresses with their ZIP Code and ZIP + 4 code.[^11] Address-matching software checks one address with [DPV](https://postalref.com/products/delivery-point-validated.md), which tells whether a ZIP + 4 coded address is a known address record in USPS's delivery file.[^12] USPS's ZIP Code Lookup finds the ZIP Code for an address, but a result does not confirm that a person or company is there.[^13][^14]

### Why can't USPS verify my address?

Address-matching software may fail to verify an address that is missing an element, because it lacks the information to find the right ZIP + 4 match.[^15] On average, 8-10% of the addresses on a list cannot be ZIP + 4 coded or DPV confirmed by CASS-certified software.[^16] USPS's [Address Element Correction](https://postalref.com/products/address-element-correction.md) service works on errors such as an incorrect street name, suffix or city name.[^17] On usps.com, an address it can't verify gets one of three messages: not found, so enter more information; a match for several more specific addresses, so choose one; or unable to verify, when some online services may not be available.[^10]

### What is USPS address validation?

Delivery Point Validation, or DPV, is the USPS product that tells whether a ZIP + 4 coded address is a known address record in USPS's delivery file.[^12] [DPV](https://postalref.com/products/delivery-point-validated.md) only checks: it adds no missing data and corrects no part of the address.[^18] USPS's Addresses API both validates and corrects address information, with data from the City State, ZIP + 4, Five-Digit ZIP, eLOT, DSF and LACSLink databases, for a price charged monthly by tier.[^19] Among [USPS's shipping APIs](https://postalref.com/guides/shipping-apis.md), the Merchant Returns API checks a customer's address with the USPS Address Validation API.[^20]

### What is USPS CASS certification?

CASS certification, from the Coding Accuracy Support System, is how USPS evaluates the accuracy of address-matching software.[^21] Any mailing claimed at an automation price must come from address lists matched and coded with CASS-certified methods.[^22] Only software and products can be [CASS](https://postalref.com/products/coding-accuracy-support-system.md) certified.[^1]

### What is AEC and how does it work?

[AEC](https://postalref.com/products/address-element-correction.md), Address Element Correction, is a computerized address correction process for business mailers.[^23] USPS runs the mailer's address list through computer logic that corrects common misspellings and other errors.[^23] Addresses AEC cannot resolve can go through [AEC II](https://postalref.com/products/address-element-correction.md#aec-ii) to delivery offices for review.[^24]

### What is the turnaround time for AEC?

AEC returns a customer's file within 48 hours after accounting approves the AEC Processing Request Form.[^23] [AEC II](https://postalref.com/products/address-element-correction.md#aec-ii), which sends unresolved addresses to delivery units, works within a 30-, 60- or 90-day window the customer picks.[^25]

### Is the AEC II service free?

No: AEC II has a set-up fee, paid through an Enterprise Payment System account or an approved credit card, and the minimum AEC service fee.[^16] The mailer also pays per record for each address that delivery unit employees resolve.[^16] As of October 4, 2026, Notice 123 prices AEC II at $59.00 for 1 to 100 records and $0.59 for each record over 100.[^26]

### Will I need to complete CASS or MASS certification again for the Intelligent Mail barcode?

No, CASS applies to mail with the Intelligent Mail barcode, and there is no need to redo the certification.[^21] [MASS](https://postalref.com/products/multi-line-accuracy-support-system.md) has an annual certification requirement, and Intelligent Mail barcode certification is part of that process.[^21]

## How it fits together

USPS keeps every delivery address in the Address Management System, the national database behind all its address correction tools.[^11] It offers address data to mailers as [Address Information System products](https://postalref.com/products/address-information-system.md), raw database files such as the ZIP + 4 Product and the City State Product.[^27] Software must use both of those products to assign and check ZIP + 4 codes completely.[^2]

Address-matching software reads those files to standardize each address and match it to its ZIP + 4, delivery point and carrier route codes.[^1] Most companies that add ZIP + 4 codes to their lists buy CASS-certified software or hire a service bureau that runs it.[^2] [CASS](https://postalref.com/products/coding-accuracy-support-system.md) is USPS's certification of that software, and MASS extends it to the machines that read addresses on mail and apply barcodes.[^21][^28] Developers can build software on USPS's own matching logic through the [Address Matching System API](https://postalref.com/products/ams-api.md).[^29]

Once an address has its ZIP + 4 code, CASS-certified software checks and completes it with the products that CASS certification includes:[^6]

- [DPV](https://postalref.com/products/delivery-point-validated.md) confirms that the address is a known USPS address record.[^30]
- [DSF2](https://postalref.com/products/dsf2.md) can take DPV's place, making the same check and adding attributes such as vacant, business or seasonal.[^6][^31]
- [LACSLink](https://postalref.com/products/lacslink.md) supplies addresses converted for the 911 emergency system.[^4]
- [SuiteLink](https://postalref.com/products/suitelink.md) adds a business's known suite number.[^5]
- The [Residential Delivery Indicator](https://postalref.com/products/address-information-system.md#rdi), whose certification is optional, tells whether an address is a business or a residence.[^6][^32]

USPS calls all of these but the Residential Delivery Indicator its licensed products, and offers them through its Licensing Department.[^33] End users get the licensed products inside a CASS-certified product.[^34] When software still cannot match an address, USPS's [Address Element Correction](https://postalref.com/products/address-element-correction.md) service corrects what it can, and AEC II sends the rest to delivery offices.[^15][^24] County and municipal addressing authorities resolve differences between their address files and USPS's database through the [County Project](https://postalref.com/products/county-project.md).[^35]

## ZIP Codes and USPS address data

ZIP Codes are 5-digit codes that identify the Post Office or delivery station for every mailing address.[^13] A ZIP + 4 code adds four digits for the sector, such as a neighborhood, and the segment, such as a building, floor or street block.[^36] Two more digits, usually the last two of the street number, make the 11-digit delivery point code.[^37] It is the finest level to which mail can be sorted by its address.[^37] The [Intelligent Mail barcode](https://postalref.com/guides/intelligent-mail.md) on a mailpiece encodes those two delivery point digits.[^37]

A complete address has every element needed to match the ZIP + 4 and City State Products exactly, down to its delivery point code.[^38] A standardized address is complete, uses USPS's official abbreviations for parts such as street suffixes, and is validated with those two products.[^39] Parts of streets with no possible delivery, such as those beside parks or railroad tracks, have no complete ZIP + 4 code.[^40] USPS's online ZIP Code Lookup finds the ZIP Code for one address, or all the ZIP Codes in a city.[^13]

USPS offers [Address Information System products](https://postalref.com/products/address-information-system.md) by annual subscription and issues them monthly through Electronic Product Fulfillment.[^41] They include these files:[^27]

- The [ZIP + 4 Product](https://postalref.com/products/address-information-system.md#zip-4-product) is the base reference that software reads to assign an address's ZIP + 4 code.[^2]
- The [City State Product](https://postalref.com/products/address-information-system.md#city-state-product) lists ZIP Codes with their city and county names.[^42]
- The [Five-Digit ZIP Product](https://postalref.com/products/address-information-system.md#five-digit-zip-product) adds ZIP Codes to mailing lists, with street detail for cities that have more than one ZIP Code.[^43]
- The [Carrier Route Product](https://postalref.com/products/address-information-system.md#carrier-route-product) gives mailers carrier route codes for presort discounts.[^44]
- The [Delivery Statistics Product](https://postalref.com/products/address-information-system.md#delivery-statistics-product) counts Post Office Boxes and business and residential deliveries for every ZIP Code.[^45]
- The [Z4CHANGE Product](https://postalref.com/products/address-information-system.md#z4change-product) shows which ZIP + 4 codes were realigned in the past twelve months.[^46]
- The [ZIPMove Product](https://postalref.com/products/address-information-system.md#zipmove-product) helps software find ZIP + 4 codes after a realignment changed a city name or finance number.[^2] A finance number is the six-digit number that identifies a USPS installation for processing its financial data.[^47]
- [eLOT](https://postalref.com/products/address-information-system.md#elot) lets mailers sort mail in about the order a carrier cases it.[^48]
- The [AIS Viewer](https://postalref.com/products/address-information-system.md#ais-viewer) is an application that retrieves, views and prints ZIP Code information for all 50 states.[^49]

> The ZIP + 4® and City/State data must be updated by ZIP + 4 and City/State product users within 45 days of the USPS® release date (ref. USPS Domestic Mail Manual).[^50]

**Must.** A user of the ZIP + 4 and City State Products must load each release within 45 days of USPS's release date.

- **ZIP Code**, also called ZIP, 5-digit ZIP Code, Zone Improvement Plan, Zone Improvement Program, ZONING IMPROVEMENT PLAN, Zone Improvement Plan Code: “a system of five-digit codes identifying the individual Post Office or metropolitan area delivery station associated with the address”[^51]
- **ZIP Code Lookup**, also called Look Up a ZIP Code: “An online application that allows a user to find a ZIP Code for a specific city or address, all ZIP Code numbers in a city, or all cities in a ZIP Code.”[^13]
- **non-deliverable**, also called ND: “Non-deliverable areas are areas to which the USPS does not deliver mail, such as vacant lots and land that borders railroad tracks.”[^52]
- **complete address**: “An address that has all the address elements necessary to allow an exact match with the current USPS ZIP+4 and City State files to obtain the finest level of ZIP+4 and delivery point codes for the address. It is normally a standardized address and contains three required address lines in order from top to bottom: recipient line (personal name or organizational name), delivery address line (street address), and last line (city, state, and ZIP Code line). It can also include an optional attention line above the recipient line.”[^38]
- **ZIP+4**, also called ZIP+4 CODE: “An enhancement to the 5-digit ZIP Code that uses an additional four digits to represent the sector (a geographic area or neighborhood) and segment (a smaller unit such as a building, floor, street block) for an address within a 5-digit zone.”[^36]
- **delivery point**, also called DP: “A single mailbox or other place to which mail is delivered. A street address does not necessarily represent a single delivery point because a street address such as one for an apartment building may have several delivery points.”[^37]
- **standardized address**: “An address that is complete, using official USPS abbreviations for elements such as directionals and street suffixes like ST or DR and state names, and validated with the ZIP+4 file and City State file.”[^39]
- **Address Management System**, also called AMS: “The national USPS database of every delivery address with its associated ZIP Code, ZIP+4 code, and city/state name that serves as the foundation of data for all address correction tools.”[^11]
- **Address Information System product**, also called AIS product: “A raw database file made available to customers to enhance address standardization, obtain detail address information, and correct address records.”[^27]

## Address-matching software and certification

CASS tests address-matching software, and only software and products can be CASS certified.[^1] A manufacturer's certification works as a blanket certification for every user of its software, and each user needs its own only in certain situations.[^3] CASS-certified software must generate PS Form 3553, the CASS Summary Report, which the mailer signs to certify how the list was coded.[^53][^54] NCOALink, an address correction service in [Move Update](https://postalref.com/guides/move-update.md), runs a CASS processing segment that gives each address its ZIP Code or ZIP + 4 code.[^55][^56]

[MASS](https://postalref.com/products/multi-line-accuracy-support-system.md) certifies the machines that read addresses on mail and apply barcodes, such as multiline optical character readers.[^57][^28] It tests whether each machine applies an accurate Intelligent Mail barcode.[^57] A machine's address-matching software must be CASS certified before anyone orders a MASS test deck for it.[^58] MASS certification lasts until the end of its annual period, from August 1 through July 31.[^28]

The [Address Matching System API](https://postalref.com/products/ams-api.md) is USPS's own address-matching engine, offered through its Licensing Department.[^33] It includes the AIS products and every licensed product but DSF2.[^33] A manufacturer may build it into its own product under a direct license from USPS.[^29] Its users must still obtain CASS certification to receive automation discounts.[^29]

> Any mailing claimed at an automation price must be produced from address lists properly matched and coded with CASS-certified address matching methods.[^22]

**Must.** A mailing at automation prices must come from address lists matched and coded with CASS-certified methods.

- **PS Form 3553**, also called CASS Summary Report: “This form may be generated as the output of address matching processing using CASS Certified™ software in conjunction with current USPS® address database files.”[^54]
- **Coding Accuracy Support System**, also called CASS, CASS software program, CASS certification process, Coding Accuracy Support System (CASS) certification: “provides hardware and software manufacturing, service bureaus, and commercial mailers a common measure by which to test the quality of address-matching software.”[^6]
- **Multi-line Accuracy Support System**, also called MASS, MULTILINE CODING ACCURACY SUPPORT SYSTEM, Multi-line Accuracy Support System (MASS) certification: “The MASS™ certification is a process similar to CASS but is designed for certification for Multiline Optical Character Readers (MLOCRs), Remote Video Encoding (RVE), and encoding stations to process address information and apply an accurate delivery point barcode (DPBC).”[^28]
- **Address Matching System Application Program Interface**, also called Address Matching System Application Programming Interface, AMS API, Address Matching System API: “AMS API is software used to develop address matching software. This software provides access to USPS® matching logic, which allows users to verify the accuracy of ZIP + 4® returns.”[^29]

## Checking and completing an address

CASS certification requires the licensed products, and end users must use them in production.[^59][^60]

| Product | When the software uses it | What it returns |
| --- | --- | --- |
| [DPV](https://postalref.com/products/delivery-point-validated.md) | Right after CASS-certified software gives the address a 9-digit ZIP Code[^61] | `Y`, `D`, `S`, `N` or blank[^62]; with the optional enhanced return codes, also `R` for an address on phantom route R777 or R779, which USPS doesn't deliver to[^63][^7] |
| [DSF2](https://postalref.com/products/dsf2.md) | In place of DPV, also right after CASS-certified software[^6][^64] | The same answers, plus attributes such as vacant or seasonal[^65][^31] |
| [LACSLink](https://postalref.com/products/lacslink.md) | When the ZIP + 4 match has an `L` in its LACS Status Indicator[^66]; also when the address matches a rural route or highway contract default, or no ZIP + 4 record, and its street is in LACSLink's street name table[^66] | The converted address[^67] |
| [SuiteLink](https://postalref.com/products/suitelink.md) | When a business address matches a street or highrise default[^3] | The suite number, when one is known[^68] |
| [RDI](https://postalref.com/products/address-information-system.md#rdi) | Optionally, with CASS-certified ZIP + 4 software[^6][^46] | `Yes` for a business or `No` for a residence[^32] |

A ZIP + 4 match places an address within a range of addresses.[^30] DPV goes one step further and confirms the address as a known USPS address record.[^30] DSF2 processing is also one approved way to put mail in [walk sequence](https://postalref.com/guides/saturation-mail.md) when the mail isn't addressed with a simplified address.[^31] A simplified address, such as “Postal Customer”, takes the place of each name and address when identical mail goes to every customer on a route.[^51]

DPV and DSF2 also carry tables that flag particular kinds of address, such as these:[^9][^69]

- A drop is a single receptacle or drop site that serves several dwellings or businesses.[^9]
- An internal drop address gets its mail through a drop address, not directly from USPS.[^9]
- No secure location means the door is accessible, but a package will not be left there for security reasons.[^70]
- Non-delivery days means mail is not delivered to the address on at least one day of the week.[^9]

Rural route and some city addresses are converted to city-style addresses so that emergency services can find them.[^71] The ZIP + 4 Product marks the records that may be converted with a LACS indicator.[^72] When LACSLink finds a converted address, CASS-certified software must return it.[^3] A suite number from SuiteLink may be left off the printed address, but to qualify for automation prices, the barcode on the mailpiece must include it.[^68]

> A Licensee or software developer writing an interface to the DPV product must first ensure the address list is processed through USPS CASS Certified software to obtain a 9-digit ZIP Code™ and a parsed address immediately prior to the validation process.[^61]

**Must.** Software that connects to DPV must first run the address list through CASS-certified software, right before validation. That run gives each address its 9-digit ZIP Code and splits it into its parts.

- **DPV = Y**, also called Y: “Address was DPV® confirmed for both primary and (if present) secondary numbers”[^63]
- **drop site**, also called drop: “A drop is a single delivery point or receptacle that services multiple businesses/families.”[^73]
- **Internal Drop Address**, also called IDA: “Addresses that do not receive mail directly from the USPS, but are delivered to a drop address that services them.”[^9]
- **No Secure Location**, also called NSL: “Flag indicates door is accessible, but package will not be left due to security concerns”[^70]
- **Non-Delivery Days**, also called NDD: “Flag indicates mail delivery is not performed every day of the week”[^74]
- **Locatable Address Conversion System**, also called LACS, Locatable Address Conversion Service: “a product/system in a different USPS® product line that allows mailers to identify and convert a rural route address to a city-style address”[^71]
- **Locatable Address Conversion System Indicator**, also called LACS indicator, LACS Status Indicator: “The LACS indicator identifies addresses in the ZIP + 4® file that may be converted to new addresses.”[^72]
- **highrise default**, also called default highrise record: “A highrise default contains the building street address in the primary range field and spaces in the secondary range field.”[^75]

## Licenses and data updates

USPS offers the licensed products through its Licensing Department.[^33] End users get this data inside a CASS-certified product, and standalone users get specially packaged data from a licensed service provider.[^34][^76]

| Product | Who may hold a license |
| --- | --- |
| [DPV](https://postalref.com/products/delivery-point-validated.md) | A CASS software manufacturer, or a company becoming one[^18] |
| [DSF2](https://postalref.com/products/dsf2.md) | A company that provides, or plans to provide, address verification and list processing services[^31] |
| [LACSLink](https://postalref.com/products/lacslink.md) | Interface developers, interface distributors and end users, each under its own license[^4] |
| [SuiteLink](https://postalref.com/products/suitelink.md) | A CASS software manufacturer or integrator, or a company becoming one, to develop an interface; a distributor, to pass the data on[^5] |
| [AMS API](https://postalref.com/products/ams-api.md) | A manufacturer, under a direct license from USPS[^29] |

USPS releases each licensed product monthly through Electronic Product Fulfillment, a secure USPS website, and only the two most recent releases can be downloaded.[^62][^77][^78][^79][^80] Customers open an account there with PS Form 5116, the Electronic Product Fulfillment Web Access Request Form.[^33][^41] A DSF2 interface stops working once its data is more than 60 days past the product date.[^64] An interface to any other licensed product stops at 105 days.[^61][^81][^82]

USPS's [National Customer Support Center](https://postalref.com/guides/getting-help.md) in Memphis offers these products and services to help mailers improve and maintain address quality.[^83]

> The licensed products cannot be shipped outside of the United States.[^33]

**Must.** A licensee must not ship the licensed products outside the United States.

- **PS Form 5116**, also called PS 5116, Electronic Product Fulfillment Web Access Request Form: “It is used to set up an account on the EPF website.”[^41]
- **Electronic Product Fulfillment**, also called EPF, Electronic Product Fulfillment (EPF) web site, Electronic Fulfillment Website: “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.”[^80]
- **End User**: “End Users are classified as customers receiving CASS Certified DPV data from a Licensed Service Provider.”[^84]
- **SuiteLink Interface Developer License**: “The SuiteLink Interface Developer License authorizes the development of Interface Products to access the SuiteLink Product.”[^5]
- **SuiteLink Interface and Data Distributor License**: “The SuiteLink Interface and Data Distributor License authorizes the right to distribute and market Interface Products and redistribute SuiteLink data to third parties.”[^5]

## Correcting addresses

[AEC](https://postalref.com/products/address-element-correction.md) works on addresses that CASS-certified software cannot match to a ZIP + 4 code.[^15] It uses Computer Logic Resolution, a program that runs evaluations and comparisons to correct insufficient addresses.[^17] AEC has an estimated correction return rate of 38%.[^23]

[AEC II](https://postalref.com/products/address-element-correction.md#aec-ii) sends the records AEC cannot resolve to the post office that serves each address.[^24] There, delivery unit employees review the bad addresses and enter corrections, which USPS calls Delivery Force Knowledge.[^16] AEC II has an average correction rate of 51%.[^24] USPS introduced it to reduce [undeliverable-as-addressed](https://postalref.com/guides/undeliverable-mail.md) mail.[^16]

USPS may correct only the addresses a mailer presents, and may not supply other address information.[^25] Mailers prepay both services by credit card or through an [Enterprise Payment System](https://postalref.com/guides/paying-postage.md) account.[^85]

The [County Project](https://postalref.com/products/county-project.md) is a free service for county and municipal addressing authorities, once a year.[^35] An authority sends its address file, and USPS returns the matched addresses standardized with their ZIP + 4 codes.[^35] Both sides then review the county codes and congressional districts that differ.[^35]

- **Address Element Correction**, also called AEC: “AEC is a process that turns problematic addresses into accurate addresses or identifies them as potentially undeliverable.”[^15]
- **Address Element Correction II**, also called AECII, AEC II Service: “AEC II is an enhancement to the existing AEC service, which identifies and corrects incomplete or inaccurate addresses using computer software. The addresses that cannot be resolved using AEC are submitted, via AEC II, to delivery offices for review and resolution.”[^24]
- **Computer Logic Resolution**, also called CLR: “CLR is a computer-based program that uses a variety of USPS programs and products to perform a series of evaluations and comparisons in an attempt to correct insufficient addresses.”[^17]
- **Delivery Force Knowledge**: “Delivery Force Knowledge leverages the efforts of local delivery unit employees who review bad addresses and enter corrections into an AEC II electronic process for return to the submitting customer.”[^16]
- **County Project**: “The County Project is for county and municipal addressing authorities working with AGT to improve address quality.”[^35]

## What goes wrong

Software that does not return a LACSLink converted address can return only the 5-digit ZIP Code.[^86] That address does not qualify for automation discounts.[^86] A mailer that purposely uses the default ZIP + 4 code in place of SuiteLink's answer risks automation discounts on the whole mailing.[^87] An unreported change to CASS-certified software can get it decertified, and USPS can then rescind discounts mailers got with it, even retroactively.[^88]

DPV and DSF2 each include a table of artificially manufactured addresses, to catch lists that were not obtained legitimately.[^89][^90] LACSLink includes one too.[^91] When an end user's list matches it, a DPV or LACSLink interface must stop processing that list.[^84][^34] A DSF2 licensee may continue, but must notify USPS of the customer's name and address at once.[^90] A one-time restart code restores processing.[^84]

An address on a phantom route, where USPS does not deliver, gets DPV's enhanced return code `R`.[^7] It gets only its 5-digit ZIP Code, with no ZIP + 4 code or DPV confirmation.[^8] Highrise and rural route default matches stay eligible for automation prices, but many of them raise delivery costs.[^75]

USPS gives a new, moved, upgraded or reassembled [MASS](https://postalref.com/products/multi-line-accuracy-support-system.md) machine a 45-day courtesy period, in which its mail can qualify for automation rates before certification.[^57][^92] A machine not certified by the end of that period becomes ineligible to submit mail at automation rates.[^92]

## Index: 71 entries

### Services (21)

- [Address Element Correction](https://postalref.com/products/address-element-correction.md)
- [Address Element Correction II](https://postalref.com/products/address-element-correction.md#aec-ii)
- [Address Information System (AIS) Viewer](https://postalref.com/products/address-information-system.md#ais-viewer)
- [Address Information System product](https://postalref.com/guides/address-matching.md#address-data)
- [Address Matching System Application Program Interface](https://postalref.com/products/ams-api.md)
- [Carrier Route Product](https://postalref.com/products/address-information-system.md#carrier-route-product)
- [City State Product](https://postalref.com/products/address-information-system.md#city-state-product)
- [Delivery Point Validation](https://postalref.com/products/delivery-point-validated.md)
- [Delivery Sequence File Second Generation](https://postalref.com/products/dsf2.md)
- [Delivery Statistics Product](https://postalref.com/products/address-information-system.md#delivery-statistics-product)
- [DPV/DSF2](https://postalref.com/products/coding-accuracy-support-system.md#terms)
- [Five-Digit ZIP Product](https://postalref.com/products/address-information-system.md#five-digit-zip-product)
- [Locatable Address Conversion System](https://postalref.com/guides/address-matching.md#verification)
- [Locatable Address Conversion Systems Linkage](https://postalref.com/products/lacslink.md)
- [Residential Delivery Indicator](https://postalref.com/products/address-information-system.md#rdi)
- [SuiteLink](https://postalref.com/products/suitelink.md)
- [SuiteLink Interface and Data Distributor License](https://postalref.com/guides/address-matching.md#licenses)
- [SuiteLink Interface Developer License](https://postalref.com/guides/address-matching.md#licenses)
- [Z4CHANGE Product](https://postalref.com/products/address-information-system.md#z4change-product)
- [ZIP + 4 Product](https://postalref.com/products/address-information-system.md#zip-4-product)
- [ZIPMove Product](https://postalref.com/products/address-information-system.md#zipmove-product)

### Programs (5)

- [Coding Accuracy Support System](https://postalref.com/products/coding-accuracy-support-system.md)
- [County Project](https://postalref.com/products/county-project.md)
- [MASS test deck](https://postalref.com/products/multi-line-accuracy-support-system.md#terms)
- [Multi-line Accuracy Support System](https://postalref.com/products/multi-line-accuracy-support-system.md)
- [Stage II](https://postalref.com/products/coding-accuracy-support-system.md#terms)

### Systems (4)

- [Address Management System](https://postalref.com/guides/address-matching.md#address-data)
- [Computer Logic Resolution](https://postalref.com/guides/address-matching.md#correction)
- [Electronic Product Fulfillment](https://postalref.com/guides/address-matching.md#licenses)
- [ZIP Code Lookup](https://postalref.com/guides/address-matching.md#address-data)

### Files (6)

- [Early Warning System](https://postalref.com/products/coding-accuracy-support-system.md#terms)
- [False Positive table](https://postalref.com/products/delivery-point-validated.md#terms)
- [False Positive table](https://postalref.com/products/lacslink.md#terms)
- [highrise default](https://postalref.com/guides/address-matching.md#verification)
- [Qualitative Statistical Summary](https://postalref.com/products/coding-accuracy-support-system.md#terms)
- [Stage I](https://postalref.com/products/coding-accuracy-support-system.md#terms)

### Identifiers (8)

- [AMS congressional code](https://postalref.com/products/county-project.md#terms)
- [AMS county code](https://postalref.com/products/county-project.md#terms)
- [Delivery Point Code](https://postalref.com/products/lacslink.md#terms)
- [Delivery Point Code](https://postalref.com/products/lacslink.md#terms)
- [Destination ZIP Code](https://postalref.com/?q=Destination%20ZIP%20Code)
- [ZIP Code](https://postalref.com/guides/address-matching.md#address-data)
- [ZIP Code prefix](https://postalref.com/?q=ZIP%20Code%20prefix)
- [ZIP+4](https://postalref.com/guides/address-matching.md#address-data)

### Documents (3)

- [Addressing Publications](https://postalref.com/?q=Addressing%20Publications)
- [PS Form 5116](https://postalref.com/guides/address-matching.md#licenses)
- [PS Form 5118](https://postalref.com/products/county-project.md#terms)

### Roles (3)

- [Commercial Mail Receiving Agency](https://postalref.com/products/delivery-point-validated.md#terms)
- [End User](https://postalref.com/guides/address-matching.md#licenses)
- [integrators](https://postalref.com/products/coding-accuracy-support-system.md#terms)

### Terms (21)

- [AEC Confidence Option](https://postalref.com/products/address-element-correction.md#terms)
- [configuration](https://postalref.com/products/coding-accuracy-support-system.md#terms)
- [Delivery Force Knowledge](https://postalref.com/guides/address-matching.md#correction)
- [delivery point](https://postalref.com/guides/address-matching.md#address-data)
- [Door Not Accessible](https://postalref.com/products/dsf2.md#terms)
- [DPV = Y](https://postalref.com/guides/address-matching.md#verification)
- [drop site](https://postalref.com/guides/address-matching.md#verification)
- [Internal Drop Address](https://postalref.com/guides/address-matching.md#verification)
- [Locatable Address Conversion System Indicator](https://postalref.com/guides/address-matching.md#verification)
- [MASS Identifier](https://postalref.com/products/multi-line-accuracy-support-system.md#terms)
- [No Secure Location](https://postalref.com/guides/address-matching.md#verification)
- [non-deliverable](https://postalref.com/guides/address-matching.md#address-data)
- [Non-Delivery Days](https://postalref.com/guides/address-matching.md#verification)
- [Official Mail Center](https://postalref.com/?q=Official%20Mail%20Center)
- [platform](https://postalref.com/products/coding-accuracy-support-system.md#terms)
- [PO Box Throwback](https://postalref.com/products/dsf2.md#terms)
- [RR](https://postalref.com/?q=RR)
- [secondary address unit designator](https://postalref.com/products/suitelink.md#terms)
- [standardized address](https://postalref.com/guides/address-matching.md#address-data)
- [zone realignment](https://postalref.com/products/address-information-system.md#terms)
- [zone split](https://postalref.com/products/address-information-system.md#terms)

## Sources

[^1]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=45), page 41: “A certification process offered to mailers, service bureaus, and software vendors that standardizes addresses in address lists and improves the accuracy of matching each standardized address to the proper delivery point code, ZIP+4 code, 5-digit ZIP Code, and carrier route code. … Only software and products can be CASS certified.”

[^2]: [Address Information System (AIS) Products Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2022-05/AIS_Technical_Guide.pdf#page=8), page 5: “Both the City State product and ZIP + 4 product are required to perform complete ZIP + 4 encoding and validation. … The majority of companies that wish to ZIP + 4 code their mailing lists either purchase commercially-available CASS Certified address-matching software or contract for CASS Certified address-matching services from a service bureau. … The ZIP + 4 product is the base reference that can be accessed by an application to assign the correct ZIP + 4 code associated with a mailing address. … This product is used to maximize mailers’ ZIP + 4 code matching potential in situations in which ZIP Code realignments have taken place and a change in city name and/or finance number has occurred (which normally prevents address-matching software from determining the newly-assigned ZIP Code).”

[^3]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=11), page 4: “DPV or DSF2 confirms whether an address is deliverable by the USPS and is mandatory for all users. … CASS offers an address matching certification process that provides the mailing industry with a method whereby a software manufacturer’s CASS certification can function as a blanket certification for all users of an address matching software package. The requirement that each user of address matching software attain CASS certification is only necessary in certain situations. … The SuiteLink product should be queried when an address matches to a street or highrise default record. … When a new LACS converted address is found the new address must be returned.”

[^4]: [PostalPro: LACSLink®](https://postalpro.usps.com/address-quality/lacslink): “The LACSLink Product is a secure dataset of converted addresses that primarily arise from the implementation of the 911 system, which commonly involves changing rural-style addresses to city-style addresses. … LACSLink has three licensing categories: … The LACSLink Developer License grants the right to develop a LACSLink interface for internal purposes and third parties. … The LACSLink Distribution License grants Developers the right to distribute the LACSLink interface and redistribute the LACSLink data. … The LACSLink End User Agreement grants the right to use the LACSLink Product to update addresses and mailing lists both internally and for third parties.”

[^5]: [PostalPro: SuiteLink®](https://postalpro.usps.com/address-quality-solutions/suitelink): “The SuiteLink® product enables customers to provide improved business addressing information by adding known secondary (suite) information to business addresses, which will allow USPS delivery sequencing where it would not otherwise be possible. … Interface Developers must be or in the process of becoming a CASS™ software manufacturer or integrator. … The SuiteLink Interface and Data Distributor License authorizes the right to distribute and market Interface Products and redistribute SuiteLink data to third parties. … The SuiteLink Interface Developer License authorizes the development of Interface Products to access the SuiteLink Product.”

[^6]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=8), page 1: “CASS certification includes DPV® or DSF2®, LACSLink®, and SuiteLink®. RDI™ certification is optional so is eLOT® with DPV certification. … provides hardware and software manufacturing, service bureaus, and commercial mailers a common measure by which to test the quality of address-matching software.”

[^7]: [DPV® Product Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf#page=14), page 14: “Address confirmed but assigned to phantom route R777 or R779 and USPS delivery is not provided.”

[^8]: [CASS™ Cycle O - Executive Summary](https://postalpro.usps.com/mnt/glusterfs/2023-03/CASS_CycleO_Executive_Summary.pdf#page=3), PDF page 3: “Identify physical addresses that are assigned to a phantom route of R777 or R779 are not eligible for USPS mail delivery. These addresses will return only a 5-Digit ZIP Code and will not be assigned a ZIP + 4® or DPV® confirmation.”

[^9]: [DPV® Product Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf#page=19), page 19: “A delivery point was active in the past, but is currently vacant (in most cases unoccupied over 90 days) and not receiving delivery. … Additional DPV Files and Descriptions … A delivery point receives mail in a single receptacle or at a single drop site that services multiple dwellings or businesses or primary or secondary addresses. … 1 – IDA (Internal Drop Address) – Addresses that do not receive mail directly from the USPS, but are delivered to a drop address that services them. … Indicates at least one day of the week mail is not delivered to the address … Addresses that do not receive mail directly from the USPS, but are delivered to a drop address that services them.”

[^10]: [USPS.com: Create Account, Account Type (as online Nov 2026)](https://reg.usps.com/register): “Fill out all the required fields and validate your address so it can be verified as a valid delivery address. … The address you've provided has been verified as a valid delivery address. … The address you provided was not found. Please try to find a more specific address by going back and entering more information. … The address you provided corresponds to a number of more specific addresses, some of which may have different ZIP+4 Codes. Please choose a more specific address from the list provided below. … We were unable to verify this address. You are able to continue, however, some on-line services may not be available for your use.”

[^11]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=13), page 9: “The national USPS database of every delivery address with its associated ZIP Code, ZIP+4 code, and city/state name that serves as the foundation of data for all address correction tools.”

[^12]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=64), page 60: “An address management product that identifies whether a ZIP+4 coded address is currently represented in USPS delivery file as a known address record.”

[^13]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=240), PDF page 240: “An online application that allows a user to find a ZIP Code for a specific city or address, all ZIP Code numbers in a city, or all cities in a ZIP Code. … A system of 5-digit codes that geographically identifies individual Post Offices or metropolitan area delivery stations associated with every mailing address.”

[^14]: [PostalPro: Look Up a ZIP Code](https://postalpro.usps.com/zip-code-lookup): “A ZIP Code result does not confirm that a person or company is at that address.”

[^15]: [PostalPro: Address Element Correction (AEC)](https://postalpro.usps.com/address-quality/aec): “If an address is missing an element, CASS Certified address-matching software may lack sufficient information to determine the correct or most accurate match to the ZIP + 4 product and, therefore, may not provide a ZIP + 4 code. … AEC is a process that turns problematic addresses into accurate addresses or identifies them as potentially undeliverable. … AEC focuses on inaccurate addresses, specifically those undeliverable addresses that cannot be matched to a USPS ZIP + 4® code using commercially available CASS Certified™ address-matching.”

[^16]: [Address Element Correction II (AEC II) FAQ](https://postalpro.usps.com/mnt/glusterfs/2024-01/QAAECII.pdf#page=1), PDF page 1: “Statistics show that on average 8-10% of address lists cannot be ZIP+4® coded or DPV® confirmed by standard CASS Certified™ address matching software. … There is a charge. … AEC II processing has an initial set-up fee that must be paid through an Enterprise Payment System (EPS) account or approved credit card, as well as the minimum AEC service fee. … In addition, the mailer will be charged per record for each resolution achieved through Delivery Force Knowledge. … Delivery Force Knowledge leverages the efforts of local delivery unit employees who review bad addresses and enter corrections into an AEC II electronic process for return to the submitting customer. … In an effort to reduce UAA, the USPS introduced AEC II.”

[^17]: [Address Element Correction (AEC) & AEC II User Guide](https://postalpro.usps.com/mnt/glusterfs/2024-01/AEC_AECII%20UG.pdf#page=5), page 4: “AEC focuses on the following addressing issues: Incomplete address Incorrect street name Missing or incorrect directional Missing or incorrect suffix Incorrect city name Incomplete building name Rural-style addresses conversion to city-style addresses … AEC programs use the ZIP + 4 and DPV products, which are updated weekly to resolve addresses by using Computer Logic Resolution (CLR). … CLR is a computer-based program that uses a variety of USPS programs and products to perform a series of evaluations and comparisons in an attempt to correct insufficient addresses.”

[^18]: [PostalPro: DPV®](https://postalpro.usps.com/address-quality/dpv): “The DPV® Product does not append any missing data or correct any address elements. … To become a licensed DPV® provider, applicant must be or in the process of becoming a CASS™ software manufacturer.”

[^19]: [DMM 509: Other Services](https://pe.usps.com/text/dmm300/509.htm): “Addresses API validates and corrects address information to improve package and mail delivery service using address data from the City State, ZIP + 4, Five-Digit ZIP, eLOT, DSF, and LACSLink databases, which are integrated into the Addresses API for a price charged monthly based on the tier, determined by the number of events.”

[^20]: [Domestic Merchant Returns API: User Guide](https://postalpro.usps.com/mnt/glusterfs/2026-07/Merchant%20Returns%20-%20Web%20Service%20and%20API%20Guide%20v2.6%202026-07-20.pdf#page=79), page 79: “The USPS® Merchant Return API uses a USPS® Address Validation API to validate the customers address passed with the request.”

[^21]: [Intelligent Mail® Barcode FAQ](https://postalpro.usps.com/mnt/glusterfs/2022-05/IMb_FAQ_5222v4.pdf#page=1), PDF page 1: “The Coding Accuracy Support System (CASS) certification enables the Postal Service to evaluate the accuracy of address-matching software programs. … The CASS process is applicable to mailpieces with the Intelligent Mail barcode, but there is no need to redo this certification. … The Multi-line Accuracy Support System (MASS) certification is an extension of CASS. It has an annual certification requirement and the Intelligent Mail barcode certification is now incorporated into this process.”

[^22]: [PostalPro: CASS™](https://postalpro.usps.com/certifications/cass): “Any mailing claimed at an automation price must be produced from address lists properly matched and coded with CASS-certified address matching methods.”

[^23]: [Address Element Correction (AEC) FAQ](https://postalpro.usps.com/mnt/glusterfs/2024-07/QAAEC.pdf#page=1), PDF page 1: “AEC is a computerized address correction process for business mailers. … The Postal Service™ runs a customer address list against the AEC program, which uses computer logic to correct common misspelling and other errors. … Customer files are returned within 48 hours after accounting approves the AEC Processing Request Form. … AEC has an estimated correction return rate of 38%.”

[^24]: [PostalPro: Address Element Correction II (AEC II)](https://postalpro.usps.com/address-quality/aec-II): “The addresses that cannot be resolved using AEC are submitted, via AEC II, to delivery offices for review and resolution. … From there, the records are sent to a post office, which services the suspected address, for possible correction. … AEC II process has an average 51% correction rate. … AEC II is an enhancement to the existing AEC service, which identifies and corrects incomplete or inaccurate addresses using computer software. The addresses that cannot be resolved using AEC are submitted, via AEC II, to delivery offices for review and resolution.”

[^25]: [Address Element Correction (AEC) & AEC II User Guide](https://postalpro.usps.com/mnt/glusterfs/2024-01/AEC_AECII%20UG.pdf#page=4), page 3: “Customers may select a processing window of 30, 60 or 90-days for their file. … The USPS is only permitted to correct addresses presented and is not permitted to provide new address information to mailers.”

[^26]: [Notice 123: Price List (effective October 4, 2026)](https://pe.usps.com/text/dmm300/Notice123.htm): “Notice 123 • Effective October 04, 2026 … 1–100 records (minimum fee) | $59.00 … Each record over 100 | 0.59”

[^27]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=12), PDF page 12: “A raw database file made available to customers to enhance address standardization, obtain detail address information, and correct address records. … AIS products include applications and electronic files such as Carrier Route, City State, Delivery Statistics, Enhanced Line of Travel (eLOT), Five-Digit ZIP, TIGER/ZIP+4, Z4Change, ZIP+4, and ZIPMove.”

[^28]: [PostalPro: MASS™](https://postalpro.usps.com/certifications/mass): “The MASS™ certification is a process similar to CASS but is designed for certification for Multiline Optical Character Readers (MLOCRs), Remote Video Encoding (RVE), and encoding stations to process address information and apply an accurate delivery point barcode (DPBC). … MASS™ certification is an annual requirement and is valid from the certification date until the end of any current annual period (i.e., from August 1 of one year through July 31 of the next).”

[^29]: [PostalPro: Address Matching System API (AMS API)](https://postalpro.usps.com/address-quality/ams-api): “AMS API is software used to develop address matching software. This software provides access to USPS® matching logic, which allows users to verify the accuracy of ZIP + 4® returns. … AMS API may be integrated within a manufacturer's product and redistributed by the manufacturer. … The AMS API Product requires a direct license from the USPS. … CASS certification is not a requirement for the AMS API Product. However, to receive automation discounts, users must obtain CASS certification.”

[^30]: [DPV® Product Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf#page=1), page 1: “Incorporating DPV with the ZIP + 4 system takes it one step further and validates the address as a known USPS address record. … A CASS Certified™ ZIP + 4 address-matching product matches and standardizes addresses within a range of addresses.”

[^31]: [PostalPro: DSF2®](https://postalpro.usps.com/address-quality/dsf2): “The DSF2® Product identifies whether a ZIP + 4® coded address is currently represented in the USPS® delivery file as a known address record. … The DSF2® Product contains vacant, residential, business or seasonal address information. … DSF2® processing is one of the approved methods outlined in the Domestic Mail Manual for sequencing mail pieces in walk-sequence when not using a simplified address. … To become a DSF2® Licensed Service Provider, applicant must be in the business of, or planning to be in the business of, providing address verification and list processing services.”

[^32]: [PostalPro: RDI™](https://postalpro.usps.com/address-quality-solutions/residential-delivery-indicator-rdi): “Addresses processed using the RDI data return an indicator denoting ‘Yes’ for Business or ‘No’ for Residential.”

[^33]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=9), page 2: “DPV® or DSF2® LACSLink® SuiteLink® The licensed products cannot be shipped outside of the United States. These products are available through the Licensing Department at AGT. … The USPS® also offers an Address Matching System Application Program Interface (AMS API) as an address matching engine through the Licensing Department at AGT. … The API includes the AIS Products, DPV®, LACSLink® and SuiteLink®. … These products are available through the Licensing Department at AGT. … To establish a CASS account, customers must complete the Electronic Product Fulfillment Web Access Request Form (PS Form 5116). … The licensed products cannot be shipped outside of the United States.”

[^34]: [LACSLink® End User Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/LACSLink_EU_LPR.pdf#page=5), page 5: “End Users are classified as customers receiving a CASS Certified product, which includes LACSLink from a CASS™ manufacturer. … Any time an address encounters a match to the False Positive table, the interface must cease the LACSLink process on addresses for the specific address list.”

[^35]: [PostalPro: County Project](https://postalpro.usps.com/address-quality/county-project): “The County Project is for county and municipal addressing authorities working with AGT to improve address quality. … The County Project's goal is to improve address quality in both of our databases by resolving addresses that differ and reviewing congressional and county code differences. … The service is free. County addressing authority may submit their file up to once a year at no cost. … County submits file on CD/DVD media via U.S. Mail or sends encrypted file via email. … Returns all matched addresses in USPS standardized address format including the ZIP+4 ultimately reducing the mailing costs associated with Undeliverable-As-Addressed (UAA) mail. … Identifies county variance records which provide the opportunity to identify specific records where the county data requires review by both the addressing authority and the USPS for possible correction. … Identifies congressional district variance records which provide the opportunity to identify specific records where the congressional district requires review by both the addressing authority and the USPS for possible correction.”

[^36]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=241), page 237: “An enhancement to the 5-digit ZIP Code that uses an additional four digits to represent the sector (a geographic area or neighborhood) and segment (a smaller unit such as a building, floor, street block) for an address within a 5-digit zone.”

[^37]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=63), page 59: “It is usually the 11-digit numeric code formed from the ZIP+4 code and the last two digits of the primary street address number (or Post Office Box, etc.) and represented by the delivery point barcode. … In mail processing and address management, the finest depth of code to which a mailpiece can be sorted by its address. … The DP is encoded within the POSTNET or Intelligent Mail barcode. … A single mailbox or other place to which mail is delivered. A street address does not necessarily represent a single delivery point because a street address such as one for an apartment building may have several delivery points.”

[^38]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=50), page 46: “An address that has all the address elements necessary to allow an exact match with the current USPS ZIP+4 and City State files to obtain the finest level of ZIP+4 and delivery point codes for the address. … An address that has all the address elements necessary to allow an exact match with the current USPS ZIP+4 and City State files to obtain the finest level of ZIP+4 and delivery point codes for the address. It is normally a standardized address and contains three required address lines in order from top to bottom: recipient line (personal name or organizational name), delivery address line (street address), and last line (city, state, and ZIP Code line). It can also include an optional attention line above the recipient line.”

[^39]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=216), page 212: “An address that is complete, using official USPS abbreviations for elements such as directionals and street suffixes like ST or DR and state names, and validated with the ZIP+4 file and City State file.”

[^40]: [Address Information System (AIS) Products Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2022-05/AIS_Technical_Guide.pdf#page=85), page 82: “Portions of a street that borders parks, railroad tracks, or other areas where there is no potential for mail delivery may have an “S” record representation in the ZIP + 4 product, but they will not have a complete ZIP + 4 code.”

[^41]: [Address Information System (AIS) Products Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2022-05/AIS_Technical_Guide.pdf#page=98), page 95: “All AIS products are offered on an annual subscription basis and are automatically issued on a monthly basis. … Address Information System products are available through Electronic Product Fulfillment (EPF). … It is used to set up an account on the EPF website.”

[^42]: [PostalPro: City State Product](https://postalpro.usps.com/address-quality/city-state-product): “City State Product is a comprehensive list of ZIP Codes with corresponding city and county names.”

[^43]: [PostalPro: Five-Digit ZIP® Product](https://postalpro.usps.com/address-quality/five-digit-zip-product): “The Five-Digit ZIP® Product provides five-digit ZIP Code™ data that can be appended to computerized mailing lists via address-matching software. … It contains 5-digit ZIP Codes and detailed, ranged street data only for cities with more than one delivery ZIP Code (i.e., multi-coded cities).”

[^44]: [PostalPro: Carrier Route Product](https://postalpro.usps.com/address-quality/carrier-route-product): “Carrier Route Product provides mailers with reference information for applying carrier route codes to addresses when taking advantage of presort postage discounts.”

[^45]: [PostalPro: Delivery Statistics Product](https://postalpro.usps.com/address-quality/delivery-statistics-product): “The Delivery Statistics Product defines the number of post office boxes and business/residential deliveries on city, rural, and highway contract routes for every ZIP Code™ in the United States.”

[^46]: [Address Information System (AIS) Products Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2022-05/AIS_Technical_Guide.pdf#page=7), page 4: “Z4CHANGE helps customers achieve this goal by providing data that indicates which ZIP + 4 codes have been realigned in the past twelve months. … The RDI product must be used in conjunction with CASS Certified ZIP + 4 address matching software and may be used on any platform.”

[^47]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=87), page 83: “An assigned six-digit number that identifies an installation or project for processing its financial data.”

[^48]: [PostalPro: Enhanced Line of Travel (eLOT®)](https://postalpro.usps.com/address-quality/elot): “The eLOT product allows mailers the ability to sort their mailings in approximate carrier-casing sequence.”

[^49]: [PostalPro: Address Information System (AIS) Viewer](https://postalpro.usps.com/address-quality/ais-viewer): “AIS Viewer is an interactive application designed to provide the ability to retrieve, view, and print accurate and current ZIP Code™ information for all 50 states.”

[^50]: [LACSLink® Software Distribution Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/LACSLink_DIST_LPR.pdf#page=6), page 6: “The ZIP + 4® and City/State data must be updated by ZIP + 4 and City/State product users within 45 days of the USPS® release date (ref. USPS Domestic Mail Manual).”

[^51]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=46), page 46: “a system of five-digit codes identifying the individual Post Office or metropolitan area delivery station associated with the address … SIMPLIFIED ADDRESS - An alternative addressing format used when delivery of identical mail is requested to every customer on a rural route or highway contract route, or to all Post Office Box customers at a Post office without city carrier service. … Instead of listing the addressee’s name and address, the mailer may use “Postal Customer.”

[^52]: [Address Information System (AIS) Products Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2022-05/AIS_Technical_Guide.pdf#page=83), page 80: “Non-deliverable areas are areas to which the USPS does not deliver mail, such as vacant lots and land that borders railroad tracks.”

[^53]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=13), page 6: “The PS Form 3553 must be computer generated from the CASS software.”

[^54]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=75), PDF page 75: “I certify that the mailing submitted with this form has been coded (as indicated above) using CASS Certified software meeting all of the requirements listed in the DMM Section 602. … This form may be generated as the output of address matching processing using CASS Certified™ software in conjunction with current USPS® address database files.”

[^55]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=4), page 1: “NCOALink is an address correction service provided to mailers through companies licensed by the Postal Service.”

[^56]: [Guide to Move Update](https://postalpro.usps.com/mnt/glusterfs/2024-01/Guide%20to%20Move%20Update.pdf#page=63), page 60: “The ‘Standardized Input’ record reference in the table below is the original address record that is appended with the correct 5-digit ZIP Code or ZIP + 4 code, other postal values and any other intelligence flags or footnotes that result from the CASS™ processing segment of the NCOALink processing job.”

[^57]: [MASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2024-10/MASS_Tech_Guide_Cycle_O.pdf#page=4), page 1: “MASS™ certification is a process designed for certification for Multiline Optical Character Readers (MLOCRs), Remote Video Encoding (RVE), Local Video Encoding (LVE), and encoding stations. … The MASS certification cycle is designed to evaluate the ability of MLOCRs and encoding stations to process address information and apply an accurate Intelligent Mail Barcode® to a mailpiece. … The Licensing and Certification Department provides a 45-day courtesy period for new, moved or relocated, upgraded, and reassembled systems.”

[^58]: [MASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2024-10/MASS_Tech_Guide_Cycle_O.pdf#page=7), page 4: “The CASS software that will be used on each representative machine must be CASS certified before a MASS test deck can be ordered.”

[^59]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=39), page 32: “DPV® or DSF2®, LACSLink® and SuiteLink® are mandatory for CASS certification.”

[^60]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=10), page 3: “ZIP +4, City State, ZIPMove and DPV or DSF2, LACSLink and SuiteLink products are mandatory for all tests. End users are required to use all these products in a production environment.”

[^61]: [DPV® Product Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf#page=4), page 4: “A Licensee or software developer writing an interface to the DPV product must first ensure the address list is processed through USPS CASS Certified software to obtain a 9-digit ZIP Code™ and a parsed address immediately prior to the validation process. … Licensees will design a process that will cause the DPV interface to stop working when the DPV data has aged more than 105 days from the product date.”

[^62]: [DPV® Product Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf#page=2), page 2: “DPV secure datasets will only provide Y, D, S, N, or blank answers … DPV updates will be provided monthly via Electronic Product Fulfillment (EPF).”

[^63]: [CASS™ Cycle O - Executive Summary](https://postalpro.usps.com/mnt/glusterfs/2023-03/CASS_CycleO_Executive_Summary.pdf#page=2), PDF page 2: “They will be available as an option for those mailers wanting the additional delineation of reasons for DPV ® Status. … Address was DPV® confirmed for both primary and (if present) secondary numbers”

[^64]: [DSF2® Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2023-11/DSF2LPR_v25_CASS_CYCLE%20O_0.pdf#page=5), page 5: “A Licensee or software developer writing an interface to DSF2 tables must first ensure the address list is processed through USPS CASS Certified software to obtain a 9-digit ZIP Code™ and a parsed address immediately prior to the DSF2 process. … Licensee will design a process that will cause the DSF2 interface to stop working when the DSF2 data has aged more than 60 days from the product date.”

[^65]: [DSF2® Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2023-11/DSF2LPR_v25_CASS_CYCLE%20O_0.pdf#page=15), page 15: “Address was DPV/DSF2 confirmed for both primary and secondary (if present) numbers.”

[^66]: [LACSLink® User Technical Reference](https://postalpro.usps.com/mnt/glusterfs/2018-03/LACSLINK_USER_TECHINFO.pdf#page=4), page 4: “If the input address matches to a record that has an “L” in the LACS Status Indicator in the ZIP + 4 file, compute the SHA of the 5-digit ZIP and fifty (50) characters address and proceed with the LACSLink lookup. … If the input address matches to a Rural Route or Highway Contract default record, query the street name table. If the RR or HC type street name appears in the table, proceed with the LACSLink lookup. … If the input address does not match a record in the ZIP + 4 file, query the street name table. … If the input street (including RR, HC or PO Box) is in the street name table, compute the SHA of the 5-digit ZIP and fifty (50) characters address and proceed with the LACSLink lookup.”

[^67]: [LACSLink® End User Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/LACSLink_EU_LPR.pdf#page=14), page 14: “LACSLink Record Match – The input record matched to a record in the master file. A new address could be furnished.”

[^68]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=121), page 114: “Given a business name and an associated ZIP + 4 coded address that matches to a highrise or street default, the SuiteLink process returns the appropriate suite number when available. … The new suite number does not have to be appended to the address for production mail but must be included in the barcode that is sprayed on the mailpiece to qualify for automation rates.”

[^69]: [DSF2® Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2023-11/DSF2LPR_v25_CASS_CYCLE%20O_0.pdf#page=1), page 1: “This product will derive other address attributes using individual tables.”

[^70]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=27), page 20: “Flag indicates door is accessible, but package will not be left due to security concerns”

[^71]: [Address Information System (AIS) Products Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2022-05/AIS_Technical_Guide.pdf#page=72), page 69: “Rural route and some city addresses are being modified to city-style addresses so that emergency services (e.g., ambulances, police) can find these addresses more efficiently. … a product/system in a different USPS® product line that allows mailers to identify and convert a rural route address to a city-style address”

[^72]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=30), page 23: “The LACS indicator identifies addresses in the ZIP + 4® file that may be converted to new addresses.”

[^73]: [Computerized Delivery Sequence (CDS) User Guide](https://postalpro.usps.com/mnt/glusterfs/2024-01/CDS_User_Guide.pdf#page=24), page 22: “A drop is a single delivery point or receptacle that services multiple businesses/families.”

[^74]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=26), page 19: “Flag indicates mail delivery is not performed every day of the week”

[^75]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=76), PDF page 76: “A highrise default contains the building street address in the primary range field and spaces in the secondary range field. … Although these addresses remain eligible for postal automation rate discounts, significant number of Highrise default/rural route default matches increases the costs and reduces the efficient delivery of this mail.”

[^76]: [DPV® Product Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf#page=8), page 8: “Standalone Users are classified as customers receiving specially packaged DPV data from a Licensed Service Provider.”

[^77]: [LACSLink® End User Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/LACSLink_EU_LPR.pdf#page=2), page 2: “LACSLink updates will be provided monthly to Licensees via the USPS Electronic Product Fulfillment (EPF) website. … There will be no more than two iterations of the monthly product updates available via EPF. Thus the two most recent product releases will be available for download.”

[^78]: [SuiteLink® Developer Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/SuiteLink_DEV_LPR.pdf#page=2), page 2: “The full SuiteLink Product datasets are provided as a flat file on a monthly basis via the USPS Electronic Product Fulfillment (EPF) website to Licensees processing in a production environment.”

[^79]: [DSF2® Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2023-11/DSF2LPR_v25_CASS_CYCLE%20O_0.pdf#page=2), page 2: “DSF2 updates will be provided monthly via Electronic Product Fulfillment (EPF).”

[^80]: [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. … 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.”

[^81]: [LACSLink® End User Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/LACSLink_EU_LPR.pdf#page=7), page 7: “Licensees will design a process code that will cause the LACSLink interface to stop working when the LACSLink data has aged more than 105 days from the product date.”

[^82]: [SuiteLink® Developer Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/SuiteLink_DEV_LPR.pdf#page=3), page 3: “Developers will design a process that will cause the SuiteLink interface to stop working when the SuiteLink data has aged more than 105 days from the product date.”

[^83]: [Address Information System (AIS) Products Technical Guide](https://postalpro.usps.com/mnt/glusterfs/2022-05/AIS_Technical_Guide.pdf#page=97), page 94: “The United States Postal Service® National Customer Support Center (NCSC) in Memphis, Tennessee is the premier resource center for business mailers. … NCSC offers a wide range of products and services that assist mailers in improving and maintaining address quality.”

[^84]: [DPV® Product Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf#page=7), page 7: “End Users are classified as customers receiving CASS Certified DPV data from a Licensed Service Provider. … Any time an address encounters a match to the False Positive table, the interface must cease validating delivery points of addresses for the specific address list. … Licensee’s software interface shall be designed to include a unique one-time only restart code to restore the processing capability.”

[^85]: [Address Element Correction (AEC) & AEC II User Guide](https://postalpro.usps.com/mnt/glusterfs/2024-01/AEC_AECII%20UG.pdf#page=6), page 5: “All AEC and AEC II are prepaid services. … AEC customers agree to make their initial payment and all subsequent payments through either a US Postal Service EPS account or valid credit card.”

[^86]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=46), page 39: “If a mailer does not return the new address from LACSLink only the 5-digit ZIP Code™ can be returned. … This address does not qualify for automation discounts.”

[^87]: [SuiteLink® Developer Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/SuiteLink_DEV_LPR.pdf#page=10), page 10: “to obtain and use the Default ZIP+4 as part of a postage discounted mailing, the entire mailing will be subject to disqualification for automation rate postage discounts.”

[^88]: [CASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2026-04/CASS%20Tech%20Guide%20Cycle%20O.pdf#page=14), page 7: “Failure of notification may result in decertification of the modified product and rescinding of any postage discounts obtained while using the modified product. … Postage discounts may be rescinded retroactively.”

[^89]: [DPV® Product Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf#page=5), page 5: “To detect conditions where address records appear to be the result of artificial manufacture, and not legitimately obtained, a table of artificially-manufactured addresses is provided as part of the product.”

[^90]: [DSF2® Licensee Performance Requirements - CASS Cycle O](https://postalpro.usps.com/mnt/glusterfs/2023-11/DSF2LPR_v25_CASS_CYCLE%20O_0.pdf#page=7), page 7: “To detect conditions when address records appear to be the result of artificial manufacture, and not legitimately obtained, a table of artificially manufactured addresses is provided as part of the product. … Any time an address encounters a match to the False Positive table, the Licensee may continue processing, but must notify USPS immediately of the customer’s name and address using the file description identified in DSF2 False Positive File Layout (Exhibit A).”

[^91]: [LACSLink® End User Licensee Performance Requirements](https://postalpro.usps.com/mnt/glusterfs/2018-02/LACSLink_EU_LPR.pdf#page=4), page 4: “To detect conditions where address records appear to be the result of artificial manufacture, and not legitimately obtained, a table of artificially-manufactured addresses is provided as part of the product.”

[^92]: [MASS™ Technical Guide for Cycle O](https://postalpro.usps.com/mnt/glusterfs/2024-10/MASS_Tech_Guide_Cycle_O.pdf#page=5), page 2: “Customers may then use the system to produce and submit mail and qualify for automation rates. … Certification must be achieved by the 45-day courtesy expiration date or adjusted courtesy date to avoid the system from becoming ineligible to submit mail at automation rates.”

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