USPS CASS address verification, explained
What CASS and DPV mean, what the codes tell you, and why suite numbers and vacancy flags decide whether a letter arrives.
Short answer
CASS (Coding Accuracy Support System) is the USPS program that certifies address-matching software. CASS-certified software standardizes an address, adds its ZIP+4 and delivery point code, and, through Delivery Point Validation (DPV), confirms whether USPS recognizes it as a real delivery point, including the suite.
What is CASS?
USPS uses the Coding Accuracy Support System to certify software that matches addresses against its national address database. A "CASS-verified" address was processed by certified software. Properly coded addresses are more likely to be delivered, and USPS requires address-quality standards for mail sent at commercial prices.
What does CASS do to an address?
- Standardizes the format. USPS spellings and abbreviations (Street becomes ST, Suite becomes STE), with the city, state and ZIP Code corrected where possible.
- Adds the ZIP+4. The extra digits narrow the ZIP Code to a block, building or group of offices.
- Adds the delivery point. Two more digits identify the exact delivery point and, with the ZIP+4, form the barcode's routing code.
- Assigns the carrier route.
| As entered | After CASS |
|---|---|
| 1187 Foundry Row, Suite 210 Columbus, Ohio 43215 | 1187 FOUNDRY ROW STE 210 COLUMBUS OH 43215-xxxx |
What do DPV codes mean, and what should you do?
Delivery Point Validation (DPV) checks whether USPS delivers to the address. An address can fall inside a valid street and ZIP+4 range and still not exist; DPV catches that.
| DPV code | Meaning | What to do |
|---|---|---|
| Y | The street address is confirmed, and so is the suite, floor or unit (or none is needed). | Mail it, once you've confirmed it's the right office. |
| S | The street address is confirmed; the suite you gave isn't. | Check the suite against the company's sources. Hold until fixed. |
| D | The street address is confirmed, but the building needs a suite and none was given. | Find the suite or floor. Hold until you do. |
| N | USPS doesn't recognize the address. | Don't mail. Research it again. |
What are the vacancy, CMRA and RDI indicators?
- Vacant. USPS records the address as unoccupied. Don't mail; the company has probably moved.
- CMRA (Commercial Mail Receiving Agency). A private mailbox at a store or mail service. Mail it only if the company publishes it, with the box number.
- RDI (Residential Delivery Indicator). Whether USPS classifies the address as residential. For B2B letters, check where it came from: a home office a business publishes is fine to mail; a home address found by looking up a person is not.
Why do suite numbers matter so much in B2B mail?
One office building can hold dozens of companies, and the suite or floor gets a letter from the mailroom to the right tenant. That's why D and S results are common in B2B lists and worth fixing. Look for the suite on the company's contact page, footer or privacy policy, its listings or its registry filing. USPS also offers SuiteLink, used by some verification providers, which adds a known suite to a business address from the company name.
Mailyard runs every address through USPS CASS. A missing or unconfirmed suite, a vacant address or one USPS can't confirm is held with the reason, and suite repair can recover a missing suite or floor. A published business address flagged as residential, such as a home office, can still mail.
How is CASS different from NCOA?
CASS checks that a delivery point is real and correctly formatted. NCOA (National Change of Address, offered as NCOALink through USPS licensees) checks whether the person or business at an address filed a change of address. It matters most for consumer mail, where households move. It does little for B2B prospecting: when a contact changes jobs, nobody files a change of address, and the old employer stays put. Re-check the contact's current employer instead.
FAQ
Does a CASS-verified address guarantee delivery?
No. It means USPS recognizes the delivery point and the format is correct. The letter still has to be addressed to the right office and suite for that person.
What's the difference between CASS and DPV?
CASS is the certification program and the overall process of standardizing and coding an address. DPV is the step that confirms the address is a real delivery point.
Should I mail an address that USPS flags as residential?
For B2B mail, only if a business publishes it as its own address, such as a sole proprietor's home office.