What CASS actually does (and why it matters).

CASS in two sentences

CASS is the Coding Accuracy Support System. It's a USPS-administered standard that vendors run mailing lists through to verify each address is real, deliverable, and standardized to USPS format.

What CASS verifies

For every address on your list, CASS:

• Confirms the address exists in the USPS database
• Standardizes formatting (123 Main St NE vs 123 Main Street Northeast)
• Adds the ZIP+4 if missing (better postage rates, faster delivery)
• Flags addresses that have moved (cross-references with NCOA — see below)
• Flags vacant addresses, PO boxes, and other deliverability issues
• Returns each address marked as "deliverable", "deliverable with corrections", or "undeliverable"

NCOA, the other half

NCOA is the National Change of Address database. The USPS reports that roughly 14% of Americans move each year. NCOA flags addresses where the resident has moved within the last 48 months and provides the forwarding address (with consent).

CASS + NCOA together is the industry-standard pre-print processing. We run every list through both. If you skip either, you're paying postage on mail that won't deliver.

The competitor problem

Most direct-mail vendors charge a $40-$80 fee for "list processing" that bundles CASS + NCOA. Some charge per-thousand-records ($5 to $15 per K). All of these are passing through software costs that run them about $0.005 per address.

We include CASS + NCOA at no extra charge. The cost was already in our process; we just stopped itemizing it.

What this means for your campaign

If your list has 1,000 addresses and you skip CASS, expect 8-15% to bounce back as undeliverable. You paid postage on those (USPS doesn't refund postage on returned EDDM, only on return-to-sender first-class). That's $30 to $80 wasted on a single 1,000-piece campaign.

CASS is the cheapest insurance in direct mail. If your vendor doesn't include it, switch.