Data Enrichment & Validation

CASS Certification Explained: Verifying the Accuracy of Commercial Zip-Code Matching

November 18, 2021
Inkit Team

According to statistics, the USPS has overseen the successful delivery of over 128 billion mails in 2021, including packages and parcels, traditional mail, marketing materials, and magazines and newspapers.

With the high number of mails being delivered every day, many companies have taken the liberty to test their mail delivery accuracy with CASS address validation. Often, the recipients fail to provide complete postal address information, which attracts costly mistakes to the postal carrier. While occasional deliveries could be verified manually, large batches usually require automated matching and verification.

CASS (Coding Accuracy Support System) is a certification product of the United States Postal Service (USPS) for verifying the accuracy of commercial zip code matching software. The USPS offers CASS certification to all mailers and software vendors seeking to evaluate the quality of their address-matching software and improve the accuracy of their ZIP+4, carrier route, and five-digit coding.

This article explains Coding Accuracy Support System (CASS) certification, who uses it, and how it helps companies obtain accurate address information.

What Is Cass Certification? Definition, Variables Tested, and Terms

Accuracy remains at the core of the USPS mailing activity. However, people often make mistakes while writing down their address information. For example, a person may provide the wrong street address, house number, or postal code. This presents a challenge to the USPS and the businesses sending various packages to customers making similar mistakes.

In order to send mails and packages to the right customer address, the USPS has to ensure that all companies referencing its database use CASS certified software.

CASS certification was introduced by the United States Postal Service USPS to help ease the pain of dealing with inaccurate information. It provides a standardized framework for all mail addresses. A typical address should be organized as follows:

  • House number/address
  • Street name
  • Name of the city
  • Name of state and the ZIP code

A CASS-certified program crosschecks the address information it has against the USPS records. While at it, the system ensures that there are no missing fields of crucial data and, more importantly, no mistakes.

Cass Certification

Thus, a CASS certification is a qualification for service bureaus, vendors, and commercial mailers that tap into the USPS database. It tests their address matching software and provides a common ground upon which these companies obtain accurate address information. Some of the variables tested in the certification include Delivery Point Validation, carrier route, and Zip + 4, just to mention a few.

The USPS provides CASS certification to mailers and companies willing to test the accuracy of their address matching software. And although companies must annually renew the certification, it helps them estimate and improve the quality of their address standardization software. The goal is to decrease undeliverable mail, unsortable mails, and extra costs of inaccurate delivery.

Which Companies Need CASS Certification?

Address Validation Service Providers

USPS provides CASS certification to service providers who offer address standardization and validation services for other companies.

A CASS-certified address validation service ensures that the customer (who is the service user) gets an updated mailing list with complete, standardized information. It achieves this by running your mail list across the USPS 30 million+ entries. Some service providers go a step further to eliminate mistakes and non-existent addresses.


Generally, a mailer doesn’t need a CASS certification if the mails it sends aren’t barcoded. But for mailers who barcode their mails, their database needs to be certified with a CASS-certifying program. Barcodes are important because they provide the most accurate mail delivery information (tracking code, serial number, mail identifier, routing code, etc.).

For small-scale mailers, it can be quite expensive to CASS-certify their mailing lists in-house. A practical solution is to outsource the work to a CASS-certified company. The process is simple: you share your list requiring verification, they cross-check it against their CASS certified software and then send it back an updated list together with a CASS report (also called Form 3553).

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Address Verification Software Vendors

Businesses that provide address validation software also need to assure their customers that their products are designed to the USPS standard. If the vendor has been CASS certified, it means that the USPS has tested the software they provide and that it provides an accurate address list.

However, software providers often have their own validation procedures. And if they feel the need to have it checked, they can simply submit it to the USPS and ask for a review. The USPS then tests the software on address validation and standardization. A yes/no answer is given depending on the results.

DPV and LACS Requirements

Delivery point validation (DPV) verifies whether a given address is actually deliverable. It checks whether the mail can be sent to the point of delivery, which is the last location the postal carrier transports the mail to. This could be a mailbox on the street or the recipient’s front door.

On the other hand, LACS (Locatable Address Conversion System) keeps a record of updated addresses for cases when, for example, a person moves to a new place. LACS converts rural route addresses to urban-style addresses, and any mail validation software seeking CASS certification is required by the USPS to reference the LACS database in its address validation process.

A system that meets these DVP and LACS requirements is ready for its CASS certificate.

CASS Processing

CASS-certified service providers perform three main functions:

  • address standardization,
  • address update,
  • address validation.
Address Standardization

Address Standardization

Address standardization usually happens right after data collection and matching. When a website asks for the user’s personal location information, the data is not always properly organized. The USPS uses a specific format that needs to be followed:

house number--street name

city--state ZIP-code

The service provider also checks for any typos and missing data. At this stage, the provider also autocompletes certain missing information such as ZIP-codes and street names provided that there is enough data.

Address Update

Now that the information has been standardized as per USPS requirements, the service provider cross-checks it against the LACS system. LACS is considered more accurate than the National Change of Address database. Although both systems work towards locating changed addresses, the LACS database is often updated to provide essential emergency services.

Address Validation

Here, the service provider checks the addresses on its system against the addresses on the USPS database. This sorts out invalid and inactive addresses.

Why Inkit Verify for Address Validation and Autocomplete

Pursuing a CASS certificate comes at an extra cost which might be too high for the average small business to pursue alone. Secondly, relying on the USPS only, you won’t receive at-scale mail verification, automation, integrations, and additional functionality that is offered by an address verification service like Inkit Verify.

Inkit Verify works with checkout forms and websites to eliminate bad address data and improve customer experience. Add address verifcation and address autocomplete software to existing forms in minutes with just a few lines of code. Start for free!

Start verifying addresses today
Don't waste time and money dealing with lost shipments that never made it to your customers.
Start for free