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CASS™ certification


The Coding Accuracy Support System, or CASS™, is a system designed to improve the accuracy of the address and ZIP Code™ that appears on each item in a bulk mailing.

Mailings that are CASS™ certified are eligible for certain bulk mail postage discounts. In order to become CASS™ certified, the mailing list must be run through a software program approved by the USPS®.

Any software that correctly formats addresses and includes accurate ZIP + 4® is eligible for CASS™ certification, but to qualify it must achieve:

  • 98.5% or higher match rate for ZIP + 4® and carrier route numbers
  • 100% for delivery point bar code extension numbers

It is important to note that CASS™ certification only handles the proper ZIP Code™, not primary or secondary information. Therefore, a CASS™ certified piece of mail may arrive in the correct city, state and ZIP Code™ but not at the correct residence because of a nonexistent house or apartment number.

Related links:

How can I ensure my mail reaches its recipients?