Sales Tax Audits in California, New York and Texas

California, New York and Texas each combine a large tax base with an active audit function, which means they have both the incentive and the staffing to examine sales tax compliance closely, especially for out-of-state sellers who've crossed economic nexus thresholds since the Wayfair decision opened the door to taxing remote sellers based on sales volume alone. If you sell into any of these three states without a local presence, don't assume you're too small to attract attention; economic nexus rules were written specifically to catch sellers who previously assumed distance was protection.

California auditors frequently focus on use tax self-assessment, meaning purchases you made without paying sales tax at the time and should have self-reported, not just tax you collected from customers. New York auditors often dig into sourcing rules for services and digital products, which have their own specific taxability rules that differ from tangible goods. Texas auditors commonly examine exemption certificates closely, checking whether every tax-exempt sale you made actually has a valid, current certificate on file rather than an expired or missing one.

Across all three states, a missing or invalid resale or exemption certificate is one of the most expensive and avoidable audit findings. If you sold something tax-free because the buyer claimed resale or exemption, and you can't produce a valid certificate for that specific sale, the auditor will generally treat it as a taxable sale and assess tax on it, even if the buyer genuinely was exempt in reality. Certificates expire, buyers change entity names, and old files get lost; review your certificate file at least annually, not just when a new large customer signs up.

For example, a seller ships a large order tax-free to a reseller and later discovers that the reseller's certificate expired before the sale. An auditor would generally treat that sale as taxable and assess the tax against the seller, even though the buyer really was a reseller. A common mistake is collecting a certificate once at onboarding and never looking at it again. The fix is an annual review that flags expiration dates and entity name changes, plus a request for a fresh certificate before the next large sale. As a decision rule, no valid certificate on file means you should treat the sale as taxable until one arrives.

Keep sales tax returns, exemption and resale certificates matched to the specific transactions they cover, a clear record of how you sourced multi-state sales, and documentation of your nexus determination for each state (when you started collecting and why). Auditors in these states will typically sample a period and ask you to substantiate specific transactions, so being able to pull the certificate or sourcing documentation for a specific invoice quickly is what actually shortens an audit, versus reconstructing it transaction by transaction under time pressure.

Keep these items ready for an auditor:

• Filed sales tax returns for each state where you collect.
• Exemption and resale certificates matched to the specific transactions they cover, reviewed at least annually for expiration.
• A clear record of how you sourced multi-state sales.
• Documentation of your nexus determination for each state, including when you started collecting and why.
• The ability to pull the certificate or sourcing support for a specific invoice quickly, since auditors sample transactions.

Don't respond to the initial information request with more than what's asked, and don't assume the auditor's first proposed assessment is final; these audits are frequently negotiated down once better documentation is produced or a sourcing dispute is resolved. Bring in a state and local tax specialist familiar with the specific state at the first notice, not after an initial assessment arrives, since early framing of the audit's scope often matters more than the paperwork produced after the fact.

If California, New York or Texas finds a real gap in your certificate file or sourcing methodology, assume the same gap exists in your other high-volume states and check it proactively rather than waiting for a second audit letter to confirm it. Companies frequently fix the audited state's specific finding and stop there, only to get the same finding a year later from a different state's auditor looking at the exact same underlying process.