What is CASS?

At A Glance

The goal of the CASS certification is to ensure the accuracy of systems using USPS data. With this level of quality control, the USPS can improve its operations by reducing undeliverable mail, unsortable mail, and parcels that require additional resources from postal workers to reach their intended destinations.

To become CASS certified, address software vendors need to undergo a test. Results are graded by the USPS and National Customer Support Center (NCSC). Upon completing the test, software developers receive useful diagnostics to help correct problems with the software.

CASS Certification

Why It Matters

The USPS maintains one of the most comprehensive and expedient mail delivery networks in the world. The backbone of the USPS is its integrated supply chain, which delivers mail to 160M+ addresses in the United States. 

Every component of a USPS address is important for communicating delivery information. According to the USPS official website, “the delivery address is the most important information on your mail piece.” 

The United States Postal Service relies on automated mail processing machines to read addresses from the bottom up. These systems first look for a city, state, and ZIP code that corresponds to a specific region within a geography. 

For businesses that reach customers in North America, failed deliveries are a multi-billion dollar problem that also creates logistical challenges for the USPS. Senders and recipients of mail can reduce strain on the Postal Service by ensuring that information is well-formatted and correct. 

Address validation, also known as address verification, is a technical process for confirming the accuracy of postal information before a piece of mail gets sent. Address verification software uses an application programming interface (API) to validate information. Data that someone enters into an online form can be checked against a dataset to validate that it is a real address. This technology is particularly useful for online retailers that engage in real-time commerce.

CASS is responsible for ensuring that the software that performs this validation is high-quality and unlikely to be returning incorrect information. The certification enables the Postal Service to evaluate the accuracy of address matching software programs in the following areas: 

  • 5-digit coding
  • ZIP + 4/ delivery point (DP) coding
  • Carrier route coding
  • DPV or DSF2
  • LACSLink
  • SuiteLink
  • eLOT
  • RDI


There are two requirements that software vendors must meet to qualify for CASS certification: using delivery point validation (DPG) and a locatable address conversion system (LACS).

DPV is a system that makes it possible to check an actual delivery destination. Address verification software, using an API, asks the USPS, “do you deliver to this location?” USPS software returns a simple yes or no response. DPV is known to be the most accurate validation technique.

LACS is a database that 911 emergency services operators maintain. It keeps tracks of locations to ensure that emergency services are deployable. Database records get updated on a regular basis.

LACS reformats addresses to conform to a national standard that makes it easier for first responders to find a location. The database also keeps track of changes to an address (i.e. a street number gets changed from an odd to an even number) to ensure that mail can be rerouted effectively.

It is important to remember that LACS is not the same as the National Change of Address (NCOA) database that tracks forwarded addresses when someone moves. NCOA tracks “who” while LACS tracks “where.”

How To Get Certified

The Canada Post also maintains an NCOA database that it licenses to third parties for verification purposes. These third parties have built software based on requirements established by the Canada post.

The CASS certification process has two stages — an optional Stage I and a mandatory Stage II.

  • Stage I is an optional self-test that helps developers assess the performance of their address-matching software. It uses a CASS test address file and helps developers with software debugging and troubleshooting. The Stage I file contains approximately 150,000 test addresses extracted from City, State, and ZIP + 4 files. There are samples included from around the United States.  The results of this test are not reviewed by the NCSC and have no effect on CASS certification.
  • Stage II is required for certification. At this stage, the CASS Department provides a test file of 150,000 sample addresses to software vendors. This test file includes addresses from across the United States.

To achieve CASS™ certification, participants must pass with a minimum score of 98.5 percent for ZIP + 4, carrier route, Five-Digit ZIP and LACSLink, 100 percent for delivery point coding, eLOT, DPV or DSF2, RDI and Perfect Address. CASS™ certification is valid until the end of the current certification period. To remain CASS™ certified for each required certification period, developers must reapply for certification and meet the minimum accuracy requirements during Stage II testing.

CASS certification is valued until the end of the current biennial period. To remain CASS certified, software vendors must repeat the Stage II testing process.


With a CASS certification, businesses have fewer moving parts to track — teams can remain confident that the address verification process will be accurate.

This accuracy is important for a number of reasons. For one, businesses with well-defined address verification processes are often eligible for postal discounts. Available only to CASS-certified businesses who ship in bulk, USPS’ worksharing discounts help businesses save money while also improving the reliability of their address information.

CASS helps interpret and correct addresses a user enters with real-world, accurate data that matches verified locations. This helps standardize addresses and reduce error. Correct addresses are critical for businesses looking to improve efficiencies.

Long-term, businesses can have more confidence in their database hygiene and accuracy. Address verification ensures that customer information is correct and usable.

Often unnoticed, address software is an important part of a digital business’s technology stack. From the customer’s perspective, this process should be taking place instantaneously and behind the scenes. There should be no delays, glitches, or bugs.

Loqate helps businesses around the world verify customer addresses by combining our global datasets with best in class technology. Our easy to integrate API helps our customers verify customer data at the point of capture. Find out more about how Loqate address verification solutions can help your business.