NCOA and CASS Certification

What is an NCOA (National Change of Address) update?

NCOA is a database maintained by the U.S. Postal Service of all individuals and companies who completed a Change of Address form in the previous four years.

Over 40 million Americans change their address each year. Outdated address information or address information that was not entered correctly, or is not in the correct USPS format are a major cause of undeliverable-as-addressed (UAA) mail.

This can lead to wasted resources and missed revenue when your mailings are not being received by your intended audience.

An NCOA update can reduce undeliverable and duplicate mail pieces by identifying incorrect addresses and correcting them prior to mailing.

National Change of Address (NCOALink) is a secure dataset of approximately 160 million permanent change-of-address (COA) records consisting of the names and addresses of individuals, families and businesses who have filed a change-of-address with the USPS". [USPS] The USPS offers licenses for Interface Developers and Interface Distributors and all NCOALink interfaces are USPS certified. There are six licenses available including Full Service Providers (48 months) and Limited Service Providers (18 months). To obtain bulk mail rates, NCOALink is required, as it reduces the number of "undeliverable-as-addressed" mailpieces, saving money and reducing the USPS's processing of this type of mail.

How does it work?

When a person fills out a Change of Address form, either online, or at the post office, first class mail is forwarded to the new address for a period of one year. This change of address information is added to the NCOA database containing more than 125 million changes of addresses. Through an NCOA service, your database is cross-referenced with the USPS NCOA Database to find moves and then updated with the newest addresses.

The addresses in the database are specifically designed to match the USPS requirements. Each entry is matched against other entries to ensure that there are no repeated addresses. The software will update your address database with the information provided by the postal service.

The Coding Accuracy Support System (CASS)

CASS certification is offered by the USPS to all mailers, service bureaus, and software vendors that would like to evaluate the quality of their address-matching software and improve the accuracy of their ZIP+4, carrier route, and five-digit coding. When choosing a vendor to process your mail, you want to make sure they are CASS certified. CASS Certification must be renewed annually with the USPS to meet current CASS Certification cycle requirements.

For more information on CASS Certification, visit the address management section of the USPS web site. CASS software will correct and standardize addresses. It will also add missing address information, such as ZIP codes, cities, and states to ensure the address is complete. Any mailing claimed at an automation rate must be produced from address lists properly matched and coded with CASS-certified address matching methods.

CASS - What gets corrected?

  • City and street name misspellings

  • Street suffixes such as Way, Court, Terrace

  • ZIP code and ZIP+4

For example:

The misspelled and incomplete address:


Is changed to:

  PASADENA CA 91103-12514

Also, in this case, the address was determined to be a business.

In addition to updating the address, CASS software can also return information about the address, such as:

  • If the address was successfully processed, or if not, then why.

  • Information on how to deliver the mailing.

CASS certification requires that vendors pass a two-stage test implemented by the USPS.

"CASS Stage I is a self-test that helps developers measure and diagnose the performance of their address-matching software when it is applied to a CASS test address file. The Stage I results assist developers with software debugging and troubleshooting in preparation for Stage II of the CASS certification process. The CASS file contains approximately 150,000 test addresses extracted from the City State and ZIP + 4 files with samples of all types of addressing used around the country. (Some test addresses have been changed for test purposes, and not all records have valid ZIP + 4 codes or valid addresses.)

Customers can evaluate the accuracy of their address-matching software by applying the correct carrier route, five-digit, and ZIP + 4 codes and by comparing the applied codes with the correct codes provided by the Postal Service. The results of Stage I processing are not reviewed by the NCSC and have no effect on CASS certification.

CASS Stage II is graded by NCSC and is used to evaluate address-matching software performance by processing a test address file. The CASS Stage II file contains approximately 150,000 test addresses that are extracted and presented in the same makeup and mixture as Stage I-only no answers are provided. Customers use their address-matching software to apply the correct codes.

Match rates using CASS Certified™ software vary greatly depending on address hygiene, the quality of addresses used, and the timeliness of the customer database update applications. An address with an incorrect five-digit ZIP™ Code, ZIP + 4 code, carrier route code, or an address with no ZIP + 4 code or failure to process using DPV or LACSLink can contribute to delays in processing mail.

To be CASS Certified, participants must pass with a minimum score of 98.5 percent for ZIP + 4, carrier route, five-digit and LACSLink. 100 percent for delivery point coding, eLOT, DPV, RDI and Perfect Address. CASS certification is valid until the end of the current annual period (i.e., from August 1 of one year through July 31 of the next). To remain CASS certified for each annual period, developers must reapply for certification and meet the minimum accuracy requirements during Stage II testing." [USPS]

See also:

Mailing Tips

USPS Postage Rates

Postage Calculator

State Postal Abbreviations

First Class or Standard Mail?

Mail Delivery Times, First Class, Standard and Non-Profit

How to Register to Business Customer Gateway

How to Download Change of Address (COA) Data

Tab Requirements for Self-Mailers

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