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Electronic Address Sequencing

Electronic Address Sequencing, or EAS, is USPS's electronic service for sequencing a mailer's address file and qualifying it for Computerized Delivery Sequence, or CDS. A list qualifies for CDS updates when it holds at least 90 percent of the possible deliveries in a ZIP Code or address group.

Updated October 31, 202628 sources

What it is

EAS is the electronic form of address sequencing, a USPS service that arranges a mailer's addresses in order of delivery. It serves mailers who can submit their address files electronically. Customers send the files to the National Customer Support Center, or NCSC, the USPS office in Memphis that processes them. Addressing & Retail Technology, at the same Memphis address, also receives the files and forms.

USPS offers these levels of address sequencing for city routes, rural routes, contract delivery service routes and PO Box sections:

  • Level 1 removes undeliverable addresses for a fee and sequences the rest at no fee.
  • Level 2 does the same and identifies where missing addresses belong, at no fee.
  • Level 3 does the same and inserts the missing addresses, for a fee.

A mailer must qualify through EAS to receive CDS. The qualification rules exist because of federal privacy laws on sharing address information. Title 39 bars USPS from giving name or address lists to anyone.

How it works

A request to qualify a list for CDS, from the list to the updates.

  1. Get an address list, made in-house or bought from an address list vendor.
  2. Run the list through CASS Certified software and keep the standardized addresses.
  3. Put the list in the EAS input format, in a file that ends in .txt.
  4. Email the zipped file to cds.ncsc@usps.gov, or mail a large file on CD/DVD.
  5. Send a Delivery Unit Summary and a Processing Acknowledgement Form with the file.
  6. The NCSC processes the file within 15 business days, in the order received.
  7. The customer receives a Detail Statement, a Not Found File when one applies, and an invoice.
  8. The customer pays the invoice within 30 days of its date.
  9. For a ZIP Code that qualifies, the customer submits a CDS Application form.

A qualified ZIP Code's addresses come back through CDS, not from the NCSC. A Level 1 or Level 2 request gets its updated file back on a CD.

Address groups

A list can try to qualify for every address in a ZIP Code or for chosen address groups. Each group the list covers has its own percentage test.

GroupShort nameThe list holds 90 to 110 percent of
City Carrier Residence-Only GroupCity Resresidential city carrier deliveries
City Carrier Business-Only GroupCity Busbusiness city carrier deliveries
City Carrier Combination Residence and Business GroupCity Allall city carrier deliveries
Post Office Box GroupPOBPost Office Box deliveries
Rural Route and Contract Delivery Service Route GroupRuralrural route and contract delivery service deliveries
Combined Delivery-Type GroupAllthe deliveries of each group it combines

Rural route, contract delivery service and PO Box groups hold both residential and business addresses, and not every ZIP Code has every group.

The forms

Every Level 3 file comes with two forms: the Delivery Unit Summary and the Processing Acknowledgement Form. The Delivery Unit Summary is the EAS application. It names the address groups the list is for, and the file holds only addresses in those groups. It also marks the level of service.

For several ZIP Codes, the form says Various in its ZIP Code box, with a spreadsheet of the ZIP Codes attached. One form covers them all. Counts by carrier route are not needed.

The Processing Acknowledgement Form comes with a signed letter on company letterhead saying how the list was developed. A list from a third party also needs a List Owner Authorization Letter from its owner. That letter says the list may go to Level 3 processing, whether seed records were added or removed, and the dates of authorized use. The forms can go by email, on CD/DVD or by fax.

The input file

The customer input file gives each field fixed positions in the record:

FieldLengthPositions
ZIP Code0502–06
Carrier ID0407–10
Primary number1018–27
Street pre-directional0228–29
Street name2830–57
Street suffix0458–61
Street post-directional0262–63
Secondary unit designator0464–67
Secondary unit number0868–75
Urbanization locale key, Puerto Rico only0690–95
Customer key05102–106

A rural route or PO Box address puts the route or box in the street name and its number in the primary number. In RR1 Box 15, RR1 is the street name and 15 is the primary number. The customer key holds any letters or digits the mailer uses to identify the record, or nothing.

One file can hold many ZIP Codes, and files on one set of media need unique names. A file holds at most 500,000 records, and a customer sends at most three files a day. An emailed file is at most 3 MB, zipped and sent as an attachment. The NCSC keeps no copy of a submitted file, so the mailer keeps its own.

The Detail Statement

The EAS Detail Statement opens with a qualification code, then the ZIP Code and the address group submitted. The qualification code is one of these:

CodeMeaning
PThe list holds at least 90 percent and less than 110 percent of possible deliveries
QAt least 90 percent of possible deliveries matched
SA seed address was found

The other columns measure the list against the ZIP Code or address group:

  • Percentage Submitted compares the addresses submitted with the possible deliveries.
  • Percentage Matched is the share of submitted addresses that match possible deliveries.
  • Addresses Submitted, Matched, Converted and Non-Existent count each kind, where converted means changed through the Locatable Address Conversion System.
  • Missing Addresses counts the addresses missing, which are added to the file when the group qualifies.
  • Fee shows the charge for the ZIP Code or address group.
  • Possible Deliveries counts the valid delivery points in USPS's database for the ZIP Code or address group.

The Not Found File

The Not Found File lists the submitted addresses that did not match USPS's database, each marked with a reason code. It comes back for ZIP Codes that fail to qualify, and never for a ZIP Code holding a seed address. The NCSC keeps it for 60 days after processing. It can hold invalid addresses, duplicates and addresses outside the address group chosen.

CodeMeaning
UNKQLThe address does not match the DSF file
BLANKA blank record
BADZPThe ZIP Code is not numeric
DEFLTA high-rise address without valid secondary information, or a rural route address without a valid box number
XSTATA physical location that receives no mail delivery, a No-Stat
NODELNot a valid delivery point
ENGNONo match in the ZIP+4 file
ENGYSA match in the ZIP+4 file but not the DSF file, perhaps from a bad primary number
ENGSNA match in the ZIP+4 file but not the DSF file, perhaps from unneeded secondary information
DUPLThe address appears in the file more than once
CSTATThe address does not receive delivery

The return file

A Level 1 or Level 2 request gets back a return file in ASCII fixed length format. Positions 11–15 hold each address's sequence number or analysis code. Positions 83–89 add the ZIP+4 sector and segment codes and the delivery point digits and check digit.

Addresses come back by ZIP Code in carrier route sequence. Within each route, the undeliverable addresses come first, then the deliverable ones in delivery sequence. In a Level 2 file, a skip in the sequence numbers marks a missing address. The file can hold invalid addresses, duplicates and addresses outside the address group chosen.

Fees

EAS charges a rate per record for each address it removes from the list and each one it adds. The fees are set in DMM 507.9 and priced on USPS Postal Explorer. The EAS fee is separate from the CDS update fee.

What a ZIP Code or address group costs depends on how far it got:

  • One that did not prequalify costs nothing.
  • One that prequalified but failed at the address level pays for removing each nonexistent address.
  • One that qualified pays for removing each nonexistent address and adding each missing one.

Rules

Customers attempting to qualify for CDS using EAS must have address lists containing at least 90 percent — but not greater than 110 percent — of the total possible deliveries in a ZIP Code.

A list sent to qualify for CDS must hold at least 90 percent, and no more than 110 percent, of the ZIP Code's possible deliveries.

Customers attempting to qualify for CDS must select service level 3 (DMM 507.9.2c), which provides sequencing of addresses, removes undeliverable addresses, and adds missing or new addresses.

A customer who wants CDS must choose Level 3, the level that also adds missing and new addresses.

Mailers must submit a completed Delivery Unit Summary (DUS) Form and Processing Acknowledgement Form (PAF) when submitting their file to the USPS in order to obtain Level 3 service for an address list.

A Level 3 file must come with a completed Delivery Unit Summary and Processing Acknowledgement Form.

If a list is leased or rented, you must receive permission from the list owner to use that list for the purpose of CDS qualification.

A mailer who rents or leases a list must get the owner's permission before using it to qualify for CDS.

All information must be left-justified within the field. Any bytes not used in the field must be left blank.

Each field's data must start at the field's first position, and the positions it does not use must be blank.

Customers are allowed a total of three attempts to qualify each ZIP Code and/or address group in a one-year period from the date of last submission.

A customer may make three attempts a year to qualify each ZIP Code or address group.

First time customers using the EAS process may submit only one ZIP Code on their first submission to ensure their file meets processing requirements and avoid unnecessary costs.

A first-time customer may send only one ZIP Code in the first file. The limit lets the customer find problems in the file before paying for a larger run.

Payment is due 30 days from the date of the invoice, regardless of qualification results.

Payment is due 30 days after the invoice date, whether or not the list qualifies.

What goes wrong

A file not in the required format does not process. NCSC staff do not reformat a file or add or delete its data.

Processing stops when the addresses submitted exceed 110 percent of the possible deliveries.

A PO Box file that includes no-stat boxes must match the box numbers exactly, with none added or left out. A miss disqualifies the ZIP Code. USPS then reprocesses it without the no-stat records, under the usual percentage test.

A seed address is a fictitious address USPS creates for a CDS customer. The customer puts it in the lists it shares, to identify them. Every ZIP Code and address group holding a seed address is disqualified, and USPS tells the list's owner and the mailer. The NCSC returns no addresses for those ZIP Codes. The mailer still pays, and USPS releases the disqualified part only on a letter from the list's owner.

Failing to qualify in three attempts in 12 months bars further attempts on that ZIP Code for one year.

A customer behind on payment cannot send more files, and qualified ZIP Codes reach CDS only once EAS is paid. Not paying within 30 days suspends CDS, and the customer must requalify.

Terms

Computerized Delivery SequenceCDS
The CDS program provides updated delivery sequence information on customer-provided address lists.
Address SequencingAddress Sequence Service
An Address Management Service in which address cards are arranged in order of delivery for city routes, rural routes, highway contract routes, and Post Office Box sections. For a qualifying mailer, address cards with either blank cards added (for missing addresses) or cards containing missing and new addresses may be added. Electronic Address Sequencing service is available for mailers who can electronically submit address files for sequencing.
possible delivery
Any stop to which a carrier could make a delivery. A possible delivery could be an active delivery point, a vacant address (designated as such if vacant for more than 90 days and flagged in the address database), or a Post Office Box throwback (designated in the address database as an address that receives free Post Office Box service at a Post Office that has no carrier delivery service or at a Post Office in which the address is within a quarter mile of the Post Office).
Processing Acknowledgement FormPAF
A mailer or a party acting on behalf of a mailer (Mailer), who submits an address list to the United States Postal Service (USPS) for Level 3 Address Sequencing Service must complete the this processing acknowledgement form (PAF).
seed address
Seed addresses are fictitious addresses created by USPS and provided to USPS® CDS customers.
Not Found File
The Not Found File contains addresses submitted by the customer that did not match addresses in the database.
National Customer Support CenterNCSC, National Customer Service Center
An organization that provides information, services, and products (e.g., address management software programs such as the City State product, zone charts, directories, testing of ZIP+4 code or delivery point code address matching software) that improve addressing quality for mailings that qualify for certain prices.
Coding Accuracy Support SystemCASS, 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.
Locatable Address Conversion SystemLACS, 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
Delivery Sequence File Second GenerationDSF2, DSF, Delivery Sequence File
The DSF2® Product identifies whether a ZIP + 4® coded address is currently represented in the USPS® delivery file as a known address record.

Documents

User Guides

Fact Sheets

Quick Service Guides

FAQs

Applications/Forms

Contacts

The EAS Service Department at the NCSC answers questions and gives technical support. It takes email at cds.ncsc@usps.gov and calls at 1-800-238-3150. Files on CD/DVD go by mail to EAS Service Department, National Customer Support Center, United States Postal Service, 225 N Humphreys Blvd Ste 501, Memphis TN 38188-1001. Forms can also go by fax to 650-357-6741.

Sources