Sales tax errors that favor the state make no noise. An underpayment eventually surfaces in an audit, with penalties attached. An overpayment surfaces never, because nobody in the system is paid to find it. States run sales tax audits to catch what you owe them, not what they owe you, and software validates its own settings. The result is a pool of recoverable refunds that grows quietly until a refund statute closes behind it. Here are the seven signs we see most often at large multistate companies, and how to claim what you are owed if three or more apply.
1. Nobody outside your company has ever reviewed your sales tax decisions
If no independent party has ever examined your sales tax decisions, assume overpayments exist. Every control points one direction: states audit for underpayment, software validates its own configuration, and internal teams review their own work. Errors in the state’s favor have no discovery mechanism, so they accumulate quietly for years.
This is not a competence problem; re-reviewing years of purchases against fifty states’ rules is nobody’s day job. One leading global food manufacturing company expected a couple million dollars from its first outside review. It found nearly $34 million across eight states; the first state approved the claim at 100 percent.
2. Your footprint changed but your tax setup did not
A tax setup built for last year’s footprint misprices this year’s transactions. New states, new products, and acquisitions all change what is taxable and where, but taxability matrices and software configurations rarely get updated at the same pace. That gap is where unclaimed refunds start accumulating.
Acquisitions are the worst offenders: you inherit another company’s tax codes and assumptions. New products are close behind. State rules diverge enough that the Streamlined Sales Tax Governing Board exists just to reduce the burden. Most common causes of sales tax overpayments trace back to a footprint change nobody translated into the tax system.
3. Capital and manufacturing purchases get taxed by default
Most states exempt or partially exempt manufacturing machinery and equipment, and many extend relief to certain capital project purchases. Vendors default to charging tax; accounts payable defaults to paying the invoice as presented. If tax routinely appears on your equipment and construction invoices, you are probably paying tax the law does not require.
Most exemptions are use-based: the same motor is taxable in the warehouse and exempt on the production line, and the vendor cannot know where it is headed. Claiming the exemption is the buyer’s job. A single mis-taxed construction contract can carry six figures of recoverable tax.
4. Tax decisions live entirely inside software nobody audits
Sales tax software executes the decisions it was configured to make; it does not question them. A wrong taxability code, a stale exemption flag, or a default mapping left over from implementation repeats on every transaction until a person finds it. Automated is not the same as audited.
Tax engines are built to file returns accurately and on time. But compliance has two halves, not underpaying and not overpaying, and software is only measured on the first. What sales tax automation misses follows a pattern: the tool is fine, the settings are where the refunds hide.
5. Exemption certificates are scattered across inboxes and shared drives
When exemption certificates live in email threads and shared drives instead of a managed repository, it costs you in both directions: tax paid on exempt purchases that you could reclaim, and assessments absorbed when an auditor requests documentation nobody can find.
Certificates expire, people leave, and institutional memory goes with them. The tell: vendors charging tax on purchases you know are exempt, and nobody able to say whether a valid certificate is on file. If pulling a certificate starts with a mailbox search, count this sign.
6. Use tax accrual is a flat estimate instead of transaction-level review
Accruing use tax as a flat percentage of purchases guarantees an error on every transaction; the only question is direction. Flat-rate accrual overpays on exempt purchases and underpays on taxable ones at the same time, leaving refunds unclaimed while still building audit exposure.
A round number feels conservative. It is not; it is untested. Overpayment and underpayment are two sides of one validation problem, and neither is visible until purchases are reviewed at the transaction level, where refunds and unrecorded liabilities turn up together.
7. Your recovery provider reports what it found, never what it checked
A recovery report that lists refunds identified but never defines the scope reviewed tells you nothing about what was missed. Findings without coverage is half an answer. Ask two questions: which transaction populations did you examine, and which states and exemption types did you test them against?
A recovery audit and a reverse audit are different exercises: the first is typically sample-driven and focused on obvious credits, the second reviews the full purchase population against each state’s rules. A provider who cannot describe what it checked has not established anything.
What to do if three or more signs apply
If three or more of these signs describe your company, commission a reverse sales tax audit of prior-period purchases: an independent, transaction-level review that quantifies what you are owed, files the refund claims, and documents where the refunds came from. Estimates and internal spot checks will not settle the question.
Refund windows close permanently: Texas, for example, generally requires claims within four years of the tax due date, and other states run similar clocks. Every elapsed month forfeits the oldest month of recoverable tax. Then fix what the review surfaces and build a standing validation framework; our complete guide to sales tax audits covers how.
Revenew’s sales and use tax recovery services work alongside your existing team and software with zero upfront cost. Request a No-Risk Review to put real numbers on these signs.
About the author: Richard Van Komen, VP, Sales Tax Recovery. He has spent 25+ years in state and local tax, formerly as a tax auditor for the Utah State Tax Commission.