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What is CASS Certification

Background and Basics

CASS (Coding Accuracy Support System) Processing tests the accuracy of address matching and correction software. The USPS offers CASS Certification to any software developer, mailer (UPS or FedEx, for example), or Service Bureau looking to improve the accuracy of their address matching software.

Address correction software is essential to getting mail where it needs to go in a timely manner. Online stores like Amazon, Wal-Mart, and Etsy run your shipping address through an address corrector during checkout, mailers like UPS and FedEx also check your address during the shipping label correction, and even GPS services like Google Maps are now able to say “You entered 123 Nain Street, did you mean 123 Main Street?” This makes sending something or going somewhere quick and easy.

But how can Amazon or Google Maps be confident that the address their software corrects to is valid and deliverable? This is where CASS Certification comes in. The USPS will provide a certificate of accuracy (CASS Certification) to any software that meets accuracy standards in the following areas:

  • ZIP coding
  • ZIP + four coding
  • Delivery point (DP) coding
  • Carrier route coding


The CASS Certification process is broken down into two stages. The first stage is self-administered and not graded by USPS. This allows developers to test and identify any issues with their software before submitting it to Stage 2 testing. In Stage 2, the software is graded by USPS and is certified if it reaches a specified % of accuracy.

Benefits of CASS Certification

Using software that is CASS Certified has many benefits:

  • Ensure that your mail is sent to a deliverable address
  • Ensure that your GPS takes you to the correct location
  • Decrease delivery times for your mail by decreasing sort times and additional time spent correcting the format of the address

Limitations of CASS Certification

Using CASS Certified software gives the best chance that your mail is delivered to the correct address in the shortest amount of time. However, like Data Point Validation (DPV), it cannot recognize a valid address entered by mistake. For example, if you sent a letter to 124 Main St. when you meant to send it to 123 Main Street, CASS Certification will not catch that mistake if 124 Main St. is a valid address. Always check your addresses before you click Submit!


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Written by Austin Proctor 


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