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Address Matching System API

The Address Matching System API, or AMS API, is USPS software that developers use to build address matching software. It gives that software USPS matching logic, so its users can verify the accuracy of ZIP + 4 returns. Manufacturers build it into their own products under a yearly license from USPS.

Updated October 31, 202613 sources

What it is

AMS API is an address matching engine that USPS offers through its Licensing Department. A manufacturer may build AMS API into its own product and redistribute that product.

The API includes four sets of USPS address data:

  • The Address Information System products, raw database files that help standardize and correct addresses.
  • DPV, which identifies whether a ZIP + 4 coded address is a known address in the USPS delivery file.
  • LACSLink, which finds new addresses after a 911 emergency system is put in place.
  • SuiteLink, data on business addresses that CASS processing finds to be highrise default records.

Files from eLOT, the product that lets mailers sort mail in about the order a carrier cases it, also work with the AMS API Developer's Kit.

What the kit holds

AMS API comes with these parts:

  • An API library for each computer platform.
  • An interface definition file, ZIP4.H.
  • A test utility, SAMPLE.EXE.
  • The test utility's source code.
  • Sample configuration data files.
  • User documentation.

How it works

The matching engine gives address matching software access to USPS matching logic and returns a standardized address. The test utility displays that address. It also checks that the Address Matching System and its data files are installed correctly.

USPS updates the AMS API Product each month through Electronic Product Fulfillment. Electronic Product Fulfillment is the secure web application that USPS uses to post Address Management and Address Information System products.

Each version of the software expires. Its .DLL files, shared objects and static objects stop working on the schedule the CASS guidelines set.

Licenses and fees

The annual license fee varies with the products and platforms a licensee uses. USPS prices AMS API together with DPV, LACSLink and SuiteLink, as a resell license or as a developer's kit.

A license year is the 12-month period the annual fee covers. For AMS API, the license year runs from October through September. As of July 16, 2026, a resell license renews at $34,300.00 a year, and each additional resell license at $17,150.00.

A renewal pays the full annual fee for the next license year. A license bought partway through the year pays a prorated fee, from the start of the next month to the end of the license year.

Rules

The AMS API Product requires a direct license from the USPS.

Anyone who uses AMS API must hold a license from USPS itself.

CASS certification is not a requirement for the AMS API Product. However, to receive automation discounts, users must obtain CASS certification.

AMS API works without CASS certification. A user who wants automation discounts must get CASS certification.

CASS developers who write their own software must subscribe to the AIS and Link Products or the AMS API prior to requesting a CASS test.

A developer who writes its own CASS software must subscribe to AMS API, or to the AIS and Link Products, before it asks for a CASS test.

All user modifications to a CASS Certified™ product must be certified separately by the end user and information about the new drivers or APIs must be listed on the CASS Order Form.

An end user who changes a CASS Certified product must certify the change separately. The CASS Order Form must list any new drivers or APIs.

Software developers must provide the static data to all end users who wish to test their software or API.

A developer must give the CASS static test data to every end user who wants to test the developer's software or API.

What goes wrong

Software built on an expired version stops working. The CASS 2006-2007 version of the AMS API Product, Cycle K, stopped working on August 1, 2007.

A CASS test that doesn't use the static test data fails. USPS revokes the certification of user-modified address matching software that the end user hasn't CASS Certified.

Terms

Address Matching System Application Program InterfaceAddress 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.
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.
Delivery Point ValidationDPV, Delivery Point Validated, delivery point valid
The DPV® Product identifies whether a ZIP + 4® coded address is currently represented in the USPS® delivery file as a known address record.
Locatable Address Conversion Systems LinkageLACSLINK, LOCATABLE ADDRESS CONVERSION SYSTEM LINKAGE
A secure dataset of converted addresses that primarily arise from the implementation of the 911 emergency location services system which commonly involves changing rural-style addresses to city-style addresses.
SuiteLinkSuiteLink Product
The SuiteLink Product is a data only product containing business addressing information specifically identified as highrise default records as a result of CASS™ processing.
Enhanced Line of TraveleLOT, eLine-Of-Travel
The eLOT product allows mailers the ability to sort their mailings in approximate carrier-casing sequence.
ZIP+4ZIP+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.
Address Information System productAIS product
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. Also called address management product.
Electronic Product FulfillmentEPF, 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.

Documents

Fact Sheets

Release Notes

Applications/Forms

Announcements

Contacts

The Addressing and Geospatial Technology office sends order forms and answers questions about AMS API at 877-640-0724. The Licensing Department at Addressing and Geospatial Technology is at 800-589-5766 and ncoalink@usps.gov.

Sources