The USPS designed the CASS certification process to test postal coding software and to influence companies to produce high-quality, addressed mail. High-quality addressed mail is mail that contains all appropriate address elements standardized in a manner regulated by the USPS. The CASS certification process tests the accuracy of the five-digit ZIP Codes, ZIP + 4 codes, and Delivery Point Barcodes that appear on mail pieces. The USPS offers postal discounts to those mailers complying with USPS addressing regulations. To qualify for these discounts, a mailer must use a CASS-certified postal coding software package to assign ZIP Codes, ZIP + 4 codes, and Delivery Point Barcodes to mailings. Software vendors supplying postal coding software must pass a test designed by the USPS in order to have their software designated as CASS-certified.
The CASS certification test is divided into two stages. The Stage 1 File is a test with answers. This stage allows processing results to be compared with those provided by the USPS and to resolve any problems before proceeding to Stage 2 testing.
Stage 2 is the actual certification process (graded by the National Customer Support Center). The Stage 2 File is a test without answers. Vendors must process the USPS-supplied file containing 150,000 address records through their software and return the file to the USPS for grading. Vendors must achieve a USPS-specified level of accuracy to be CASS-certified. The table below details the levels of CASS certification and the accuracy requirement for each level.
| Certification Level | Required Accuracy Level |
|---|---|
| ZIP | 98.5% |
| Carrier Route | 98.5% |
| ZIP + 4 | 98.5% |
| Delivery Point Barcode | 100% |
| eLOT | 100% |
| Perfect Addresses | 100% |
CASS certification is valid through the end of the current CASS cycle. Vendors must apply and achieve a specified level of accuracy for each CASS cycle. In addition to the above overall percentages, address matching software must attain a 98.5% rating in all required categories.