Sales tax compliance has a standard definition: register where you have nexus, collect the right tax, and file on time. Every software vendor and accounting firm will give you some version of that answer. It is accurate, and it is incomplete. A program built only to satisfy filing deadlines can pass a sales tax audit and still leave refunds unclaimed, because the same weak controls that create underpayment exposure also let overpayments go unnoticed. The state sends a notice when you underpay. Nobody sends one when you overpay.
This article lays out how to build an internal sales and use tax compliance program that holds up on both sides: who owns it, the controls that do the work, the review cadence that keeps them honest, and the measures that tell you whether any of it is working. It is written for tax, finance, and procurement leaders at multi-state enterprises, where transaction volume is high enough that unclaimed refunds compound fast.
What sales tax compliance actually covers
Sales tax compliance is the set of processes a company uses to meet its sales and use tax obligations: registering where it has nexus, charging correct tax on sales, accruing use tax on untaxed purchases, filing accurate returns on time, and keeping documentation to prove it. A complete definition also includes not paying more than the law requires.
The first half of that definition is well understood because it is enforced. States assign your filing frequency and calendar when you register, and the deadlines are unforgiving. In Texas, for example, returns are due on the 20th of the month following the reporting period, every late report draws an automatic $50 penalty, and tax paid late adds a 5 or 10 percent penalty on top. Multiply that discipline across every state where you file and it is obvious why compliance teams organize their lives around the filing calendar.
The second half is the blind spot. The scale of the system practically guarantees errors in both directions: there are more than 11,000 standard sales tax jurisdictions in the United States, according to Tax Foundation data, and Vertex counted 681 sales tax rate changes and new rates in 2025 alone. Some of those errors mean you collected or remitted too little, and an auditor will eventually find them. Others mean you paid tax on exempt purchases, applied the wrong rate, or accrued use tax on transactions that were never taxable. No enforcement mechanism exists for those. Underpayment and overpayment are two sides of the same validation problem, and a program that only checks one side is doing half its job.
Who owns sales tax compliance
No single function owns sales tax compliance end to end in most large companies. Tax owns returns and audits, accounts payable executes the payments tax rides on, procurement shapes the contracts and vendor relationships, and IT maintains the systems that calculate everything. The most common structural weakness is not a missing control but a missing owner.
Each function holds a real piece of the program. The tax team makes nexus determinations, sets taxability positions, and files returns. Accounts payable decides, hundreds of times a day, whether to pay invoices exactly as billed, which makes it the last line of defense against vendor-charged tax that should never have been charged. Procurement determines whether contracts state tax treatment clearly and whether vendors receive the exemption documentation they need before the first invoice. IT owns the tax codes, rate engines, and system mappings that turn all those decisions into numbers.
The accountability gap appears in the seams. When compliance is everyone’s job, an AP processor pays the tax as billed because questioning it is not in the job description. Procurement signs a contract that never mentions tax treatment. IT carries forward a tax code mapping from an implementation nobody remembers. Each function reasonably assumes another one is checking. The fix is not heroic effort; it is a named accountable owner, usually a tax director or controller, with the other functions’ responsibilities written down and reviewed, so that no taxability decision gets made by default.
The control set: five disciplines that do the work
A durable sales tax compliance program rests on five controls: registration and nexus monitoring, documented taxability matrices, exemption certificate management, use tax accrual discipline, and routine reconciliation of tax accounts. Each control prevents a specific failure mode, and each one degrades quietly when nobody is assigned to maintain it.
- Registration and nexus monitoring. Since the Supreme Court’s 2018 decision in South Dakota v. Wayfair, physical presence is no longer required for a state to impose collection obligations; the Court upheld South Dakota’s threshold of $100,000 in sales or 200 transactions, and states have since enacted their own economic nexus rules. Your footprint now changes with your revenue, not just your real estate. Review nexus at least annually against sales by state, headcount, inventory locations, and contractor activity.
- Taxability matrices. Document how every product and service line is treated in every state where you operate, with the legal basis for each position. An undocumented taxability decision is not a position, it is a guess that will be re-litigated from scratch at audit. Matrices need an owner, a date, and a trigger for review when offerings or laws change.
- Exemption certificate hygiene. Missing or expired certificates from customers create audit exposure; failing to issue your own certificates to vendors creates overpayment. Both failure modes come from treating certificates as paperwork instead of as a control, and both are addressed by the practices covered in our guide to exemption certificate management.
- Use tax accrual discipline. Use tax compliance is where programs most often fail in both directions at once. Untaxed purchases that should be self-assessed create audit exposure, while blanket accrual rules quietly assess tax on purchases that qualify for exemptions. Accrual logic deserves the same documentation and review as sales-side taxability, because auditors test one side and nobody tests the other.
- Reconciliation of tax accounts. Tie tax accrual and payable accounts in the general ledger to filed returns and to source-system detail every month. Unexplained variances are how you discover a broken tax code, a duplicated accrual, or a rate mismatch while the fix is still cheap.
Review cadence: monthly, quarterly, annually
A working review cadence has three layers: monthly reconciliation of tax accounts against filed returns, quarterly review of taxability positions and certificates against business and law changes, and annual independent validation of the whole program. The monthly layer catches errors, the quarterly layer catches drift, and the annual layer catches what internal reviews cannot.
Monthly reconciliations are the floor. If the general ledger, the returns, and the source systems do not tie, nothing downstream can be trusted, and variances should be investigated whether they run in the state’s favor or yours.
Quarterly reviews exist because the environment does not hold still. New products launch, operations expand into new states, vendors change billing systems, and jurisdictions change rates and rules by the hundreds each year. A taxability matrix or nexus analysis reviewed annually is guaranteed to spend most of its life out of date.
Annual independent validation is the layer most programs skip, and it is the one that finds the money. The people who built the controls are structurally the wrong people to find their blind spots, which is why sales tax audits so often surprise well-run teams. A reverse sales tax audit, a systematic review you initiate to find tax you overpaid, applies audit-grade scrutiny to the side of compliance no state will ever check for you, and is typically structured as a no-risk review with zero upfront cost.
Technology’s role and its limits
Tax engines and filing software are necessary for multi-state sales tax compliance, and they are good at what they were built for: applying rates, tracking deadlines, and producing returns at scale. They are not built to question their own inputs. A misconfigured tax code, a stale exemption, or a vendor’s billing error passes through automation untouched.
This is the structural reason software-first programs leave refunds behind. Automation optimizes for the filing side of compliance because that is the side with deadlines, penalties, and enforcement. The determinations that drive the output, taxability mappings, exemption flags, accrual rules, were made by people at implementation and then aged in place. When the business changes and the configuration does not, the engine keeps executing yesterday’s decisions with perfect consistency. The errors it produces are systematic, which means they are also large: the same wrong mapping applied to every transaction, every month, in every state. We cover the specific gaps in detail in what sales tax automation misses.
The conclusion is not to distrust your tools. It is to treat them as executors of decisions rather than makers of them, and to schedule human review of the decision layer: the mappings, matrices, and rules the software runs on.
Preparing for the audit you will eventually get
If you operate in multiple states, a sales tax audit is a matter of when, not whether. Audit readiness means producing registrations, returns, workpapers, exemption certificates, and use tax accrual support for the full lookback period, typically three to four years, without a scramble. The records that defend you against assessments are the same ones that document your overpayments.
A program built on the controls above is most of the way to audit-ready, because the auditor’s requests map directly onto them: show me your nexus analysis, your taxability positions, your certificates, your accrual logic, your reconciliations. What remains is response discipline, knowing who manages the auditor relationship, how sampling will be negotiated, and where the sensitive judgment calls live, which we walk through in how to prepare a sales tax audit defense.
There is a second reason to prepare early. The statute of limitations runs in both directions: the same clock that limits the state’s lookback also closes your refund window, month by month. Companies that review their own transactions on the state’s schedule, only after the audit notice arrives, routinely discover overpayments they can no longer claim.
How to measure program health
Measure a sales tax compliance program on four dimensions: filing performance, meaning on-time rates and penalty dollars; audit outcomes, meaning assessments as a share of tax remitted; recovery findings, meaning overpayments identified per review cycle; and control coverage, meaning the share of spend flowing through documented taxability and accrual rules. Tracking only the first is measuring half the job.
Filing performance and audit outcomes are the familiar metrics, and mature teams already watch them. Recovery findings are the uncomfortable addition. A program that has never identified an overpayment is not necessarily clean; more often, nobody has looked. Treat recovered dollars as a diagnostic, not just a windfall: every finding points at an upstream control that failed, and feeding those findings back into matrices, accrual rules, and system mappings is what converts a one-time recovery into a permanent fix. Over time the health signal you want is a specific trajectory: findings that spike on the first independent review, then decline as root causes get corrected, while control coverage climbs.
About the author: Richard Van Komen, VP, Sales Tax Recovery. He has spent more than 25 years in state and local tax and is a former tax auditor for the Utah State Tax Commission.
An independent review is the fastest way to learn whether a program tuned for filing deadlines has been leaving refunds unclaimed on the overpayment side. Revenew’s sales and use tax recovery services work alongside your internal team and existing providers with zero upfront cost. Request a No-Risk Review.