You collected the resale certificate. Good. Is it actually valid?
Most sellers stop at "we have a PDF on file." In an audit, that's not the test. The auditor's test looks more like this.
1. The right form for the right state
Many states require their own form — New York's ST-120 won't cover a New Jersey sale. Some accept the MTC or SST multistate forms; some don't.
2. Every field completed
Buyer's legal name and address, your name as seller, what's being purchased, the reason for exemption. Blank fields are the most common defect.
3. A plausible registration number
Each state has its own ID format. A number that doesn't match the state's pattern is a red flag you can catch in seconds.
4. Signed and dated
Unsigned certificates come in more often than you'd think.
5. Not expired
Some states' certificates lapse, and blanket certificates in particular need a renewal calendar rather than a folder. Florida's annual resale certificate expires every December 31; Washington reseller permits run four years; Connecticut blanket certificates should be renewed roughly every three years. New York and Pennsylvania blanket certificates generally stay valid until revoked or the underlying facts change. Check the states you actually sell into rather than assuming — the rules genuinely differ.
6. The number checks out with the state
Several states publish lookup tools — Texas's Sales Taxpayer Search and California's "Verify a Permit, License, or Account" are two well-established ones. Where one exists, use it.
Run the checks at the right moment
Do this when you accept the certificate — not three years later with an auditor across the table. And if a buyer hands you an EIN or a W-9 instead of a certificate, that's a different document with a different job.
Our free validator runs the document-level checks — form, fields, ID format, expiration — with the rule citations behind each one, in about 30 seconds. Checking numbers against state-published registry data (TX & PA today) is part of our plans.
General education, not tax advice — your state's Department of Revenue or a SALT professional is the authority for your situation.