USPS CASS certification: what it means and why it matters for your data

If you've shopped for address validation, you've seen "CASS" on every vendor's website, usually inside a badge. Few of them explain it.

They should, because CASS is the closest thing the US has to a referee for address data. It's how the Postal Service checks that a piece of software matches addresses the way the USPS itself does. If your business ships or mails anything, it's worth knowing what the badge covers and what it doesn't.

What is USPS CASS certification?

CASS stands for Coding Accuracy Support System. It's a USPS certification program for address-matching software. Vendors submit their software, the USPS tests it against a set of addresses, and software that scores high enough is certified for the current cycle.

The current cycle is Cycle O, and its certifications are valid through July 31, 2028. When a cycle ends, the software has to be tested again.

The tests cover:

• 5-digit ZIP Code and ZIP+4 coding
• Delivery point coding
• Carrier route coding
• Delivery Point Validation (DPV), or DSF2
• LACSLink and SuiteLink updates
• eLOT, the line-of-travel sequence mailers use for carrier route sorting
• RDI, the Residential Delivery Indicator

The bar is high. Software needs 98.5% accuracy on ZIP+4, carrier route, 5-digit and LACSLink coding, and 100% on delivery point coding, eLOT, DPV or DSF2, and RDI.

What does CASS check?

DPV is the one I'd ask about first. ZIP+4 coding can tell you an address falls in a valid range on a valid street. DPV tells you whether the USPS actually delivers to that specific address.

Who needs CASS-certified addresses?

If you send mail at automation prices, CASS is a requirement. Under the USPS Domestic Mail Manual, addresses must be coded with CASS-certified software using a USPS data release that's still within its product cycle. There's no fixed day count; the data has to be current. Each automation-price or carrier-route-price mailing also needs a PS Form 3553, the CASS Summary Report, which documents how the list was coded.

If you ship parcels, nobody asks you for a CASS report. The carriers do charge you when an address is wrong, though: $25.50 per correction at FedEx and $25.25 at UPS in 2026 (here's how those fees add up). Running addresses through CASS-certified matching before the label prints catches many of those errors while they're still free to fix.

If you run a CRM or a customer database, standardized addresses make duplicates easier to find and segments easier to trust. "123 Main Street, Apt 4" and "123 MAIN ST #4" become the same record.

What's the difference between CASS and NCOA?

CASS confirms an address is valid and deliverable. NCOALink, the USPS change-of-address service, tells you whether the person you're trying to reach has moved. An address can pass every CASS check and still be wrong for your customer, because they left two years ago.

People move a lot. The Census Bureau's American Community Survey found 11.8% of people moved in 2024, and in states like Colorado and Texas it was closer to 14% (every state is here). The USPS processed 71,130 address changes a day in 2025.

Mailers who claim automation or presort prices have to meet the USPS Move Update standard, which means updating addresses within 95 days before the mailing, using an approved method such as NCOALink or ACS. Address validation and change-of-address processing are separate services, so check which one you're buying.

How do you check a vendor's CASS claim?

The USPS publishes its certified product lists on PostalPro, including software manufacturers and service bureaus for the current cycle. Checking a claim takes a few minutes:

1. Find the vendor, or the software they use, on the current Cycle O list.
2. Check which functions are certified. DPV, LACSLink, SuiteLink and RDI are each listed separately.
3. Ask whose certification it is. Some providers hold it themselves. Others run certified software from a USPS licensee. Both are legitimate, but the wording should say which.
4. If you mail at automation prices, ask whether they can give you a PS Form 3553 for your list.

Where DQVerify stands

DQVerify address validation processes US addresses with USPS CASS Certified software supplied by a USPS licensee. Each US check corrects and returns the ZIP+4 and confirms deliverability with DPV. The certification belongs to that software, not to DQVerify, and you should know that before you buy from us or anyone else.

CASS is a US standard, so it applies to US addresses only. For international addresses, DQVerify covers 240+ countries and territories using licensed postal data. You can run checks through the API as customers type, or upload a CSV of your list. Native Salesforce and Shopify connectors come with Enterprise plans. If you run deliveries, the logistics page shows where the check sits before dispatch.

You get 100 free credits for 14 days to test it on your own records, and pricing is per check after that, with no subscription. Whichever vendor you pick, ask them step 3 above and make sure the answer is in writing.