Postal Optimization
CASS vs. NCOA: What Marketers Actually Need to Know
CASS fixes and verifies addresses. NCOA updates addresses for people who moved. What each does, why the USPS Move Update standard matters, and what neither one can do.
AVS Leads · · 3 min read
CASS and NCOA show up on every mailing list quote, often together, and are easy to confuse. They solve two different problems. You usually need both.
The short version
| At a glance | CASS | NCOA |
|---|---|---|
| Question it answers | Is this a real, correctly formatted address? | Does this person or business still live there? |
| What it changes | Spelling, abbreviations, ZIP Code, ZIP+4, delivery point codes | The address itself, when a move was reported |
| Why it matters | Deliverability and presort/automation price eligibility | Fewer pieces sent to the wrong place; Move Update compliance |
What CASS does
CASS (Coding Accuracy Support System) is the USPS program that certifies address-matching software. When a list is run through CASS-certified software, each address is compared to USPS address data. Street names and suffixes are corrected, ZIP Codes are verified, ZIP+4 and delivery point codes are added, and addresses that cannot be matched are flagged.
Delivery Point Validation (DPV) is often run alongside CASS to confirm that the address is an actual delivery point, including the apartment or suite where one applies.
What NCOA does
NCOA processing compares your list to the USPS change-of-address data available through the NCOALink system, which the USPS describes as a dataset of approximately 160 million permanent change-of-address records. When a match is found, the new address is returned where one is available.
NCOA only knows about moves that were reported to the USPS. People who move without filing a change of address will not be caught.
The Move Update standard
The USPS requires mailers claiming presorted or automation First-Class Mail prices, and USPS Marketing Mail prices, to show that addresses were updated within 95 days before the mailing date using an approved method. NCOALink processing is one of the approved methods; Address Change Service (ACS) and certain ancillary service endorsements are others.
In practice: if a list is being mailed at commercial prices, move-update it close to the mail date.
Why you need both
CASS makes sure the address is valid. NCOA makes sure it is still the right address for that person. A perfectly formatted address for someone who moved two years ago is still waste, and so is a current resident at an address with a typo the equipment can't read.
What neither one does
- It doesn't make a poorly targeted list a good one.
- It doesn't catch moves that were never reported.
- It doesn't remove duplicates. That's merge/purge.
- It doesn't guarantee a postage price on its own. Eligibility depends on all USPS requirements for the mailing.
Next step
If your list hasn't been processed recently, or you're not sure, send it to us before your next mail date. We will tell you what CASS and NCOA would change. Learn more about CASS & NCOA processing.
Sources
- USPS PostalPro: Move Update (accessed September 2026)
General information only. Postal standards and legal requirements change; confirm current rules before each campaign. Questions? Talk to a data expert.