Quick overview

State audits of out-of-state sellers examine whether a remote business correctly collected, reported, and remitted sales and use taxes in states where it has economic or other forms of nexus. After the Supreme Court’s decision in South Dakota v. Wayfair, Inc. (2018), states have expanded enforcement against remote sellers. Audits can be triggered by data matches, marketplace sales reporting, third-party leads, or routine compliance sweeps.

Why states audit remote sellers

States seek tax revenue and fairness between in-state and out-of-state sellers. Audits help state revenue departments:

  • Confirm a seller’s nexus and registration status.
  • Verify that taxable sales were properly collected and remitted.
  • Identify unreported liabilities, interest, and penalties.

In my work advising online retailers and SaaS providers, I see two recurring drivers for audits: (1) economic nexus thresholds that force registration and collection obligations, and (2) marketplace facilitator reporting (marketplaces now often report seller sales directly to states). After Wayfair (138 S. Ct. 2080 (2018)), many states adopted economic nexus rules; thresholds commonly are $100,000 in sales or 200 transactions, though some states use different amounts or tests. Always check each state’s statute or guidance.

Common triggers that start an audit

  • Data matches or third-party reporting from marketplaces and payment processors.
  • Large year-over-year sales increases into a state where you’re not registered.
  • Customer complaints or whistleblower tips.
  • Random compliance programs and targeted reviews for specific industries.

Marketplaces (Amazon, Etsy, eBay) and payment processors increasingly share data with states. That can flag unregistered sellers quickly. For nexus basics and tests you can compare, see our State Sales Tax Nexus resources such as “State Sales Tax Nexus: Practical Tests for Remote Sellers in 2025” and our “Nexus Checklist for Online Marketplaces: When to Register in a State.” (These cover thresholds, registration guidance, and changes that matter for audits.)

Typical audit types and scope

  • Desk audits: The state requests documents and reconciliations by mail or electronically. These are the most common for out-of-state sellers.
  • Field audits: An examiner visits your location or your representative’s office to inspect books and records.
  • Focused or industry audits: Targeted reviews for sellers in high-risk sectors (e.g., remote sellers in high-volume categories).

Scope usually covers a set of tax periods (commonly 3–6 years) but can extend further if the state alleges fraud or willful concealment. Each state sets its own statute of limitations and rules, so ask the examiner to confirm the exact audit window.

What auditors will ask for (prepare these promptly)

  • Sales journals and general ledger summaries for the audit period.
  • Customer invoices and order records showing ship-to addresses and product/service descriptions.
  • Exemption certificates and resale certificates (for tax-exempt sales).
  • Purchase orders, contracts, and shipping documents.
  • Marketplace settlement reports and payment-processor statements.
  • Sales tax returns and proof of remittance (cleared checks, ACH records).
  • Records of returns, credits, and bad-debt write-offs.

Tip: Keep a reconciliation that maps gross sales to taxable sales and to sales tax collected. A clean reconciliation saves time and reduces the likelihood of proposed assessments.

How the state analyzes data

Auditors compare reported taxable sales and sales tax remitted to transaction-level records, marketplace reports, and third-party data. Common analytical methods include:

  • Sampling: Reviewing a representative sample of transactions and extrapolating results.
  • Data matching: Cross-referencing marketplace facilitator reports or 1099-K-like information with filed returns.
  • Product classification review: Determining whether items sold are taxable or exempt.

States increasingly use automated tools and data feeds; accurate, searchable records make audits less disruptive.

Possible outcomes and financial effects

  • No change: Records support reported liabilities.
  • Adjustment with additional tax due: The state proposes additional tax, plus interest and possible penalties.
  • Voluntary Disclosure Agreement (VDA) option: If you discover unregistered nexus and proactively contact the state, some states offer VDAs to limit the look-back period and reduce or waive penalties.

Penalties and interest vary by state. Interest typically accrues from the original due date; penalties can range from a percentage of the unpaid tax to greater amounts for fraud. If you can show reasonable cause or reliance on professional advice, some penalties may be waived.

Steps to take immediately after receiving an audit notice

  1. Read the notice carefully for deadlines and the documents requested.
  2. Don’t ignore the notice — silence can lead to default assessments.
  3. Gather the requested records and start an internal reconciliation.
  4. Consider hiring a state and local tax (SALT) expert or CPA experienced with multi-state audits.
  5. If you need time, request an extension in writing; auditors frequently grant reasonable extra time when asked promptly.

In my practice, swift organization and early communication with the auditor often narrow the scope and reduce proposed assessments.

Strategies to limit exposure

  • Register and collect voluntarily in states where you meet nexus thresholds — that reduces penalty risk later.
  • Maintain robust exemption certificate management and a reliable process for storing certificates.
  • Track marketplace and dropshipping flows carefully; know who is the taxable seller under applicable laws and contracts.
  • Perform internal sales tax health checks annually and reconcile marketplace reports to your books.
  • Use voluntary disclosure programs when appropriate to secure limited look-back periods and penalty relief.

For sellers using marketplaces, our guide “State Sales Tax Nexus for Online Sellers: Establishing and Managing Obligations” explains registration and compliance steps that reduce audit exposure: https://finhelp.io/glossary/state-sales-tax-nexus-for-online-sellers-establishing-and-managing-obligations/

Common mistakes that worsen audit outcomes

  • Failing to keep legible, transaction-level records for each sale.
  • Assuming marketplace facilitators eliminate all seller obligations (marketplace laws vary by state).
  • Not confirming the legal seller for dropship and fulfillment arrangements.
  • Missing timely responses to audit requests.

Appeals and closing the case

If you disagree with a proposed assessment, you can file an administrative protest or appeal within the timeline specified by the state. Work with counsel or a SALT specialist to prepare a concise position with supporting documentation. Many disputes resolve by negotiation — for example, by narrowing the audit period, accepting limited adjustments, or entering a payment plan.

Documentation best practices going forward

  • Store invoices, shipping records, and exemption certificates for at least the longest applicable state statute of limitations (commonly 3–7 years).
  • Maintain clear mappings of where sales were shipped or delivered, and save marketplace settlement reports.
  • Keep a written nexus evaluation for each state annually and when business models change.

Authoritative references and where to check next

  • The U.S. Supreme Court decision, South Dakota v. Wayfair, Inc., 138 S. Ct. 2080 (2018) established modern economic nexus rules.
  • Check state revenue department websites for audit procedures, nexus thresholds, and voluntary disclosure programs (rules vary by state).
  • General federal tax guidance is available from the Internal Revenue Service (irs.gov). For consumer and marketplace reporting contexts, consult the Consumer Financial Protection Bureau (consumerfinance.gov).

Final checklist before an audit

  • Assemble the last 3–6 years of sales and tax records, plus marketplace reports.
  • Prepare reconciliations that link gross sales to taxable sales and tax collected.
  • Identify and locate exemption certificates and resale documentation.
  • Decide whether to engage a SALT specialist or CPA.
  • Consider voluntary registration or VDA if you identify unreported nexus.

Professional disclaimer

This article is educational and reflects general practices as of 2025. It is not legal or tax advice. For specific guidance about an audit or your state’s rules, consult a qualified tax professional or attorney familiar with state and local tax (SALT) matters.

If you’d like, I can provide a short checklist tailored to either (a) a marketplace seller, (b) a dropshipper, or (c) a SaaS/digital service provider to help prioritize records and next steps.