State Tax: Defending Complex Nexus Determinations and Audit Risk

Most states have enacted economic nexus thresholds modeled on the South Dakota standard of $100,000 in annual sales or 200 separate transactions, either of which independently creates an obligation. Once either threshold is crossed, the seller must register, collect, and remit sales tax to that state beginning the next calendar quarter or following month, depending on the state's specific rule. State and local tax counsel reviewing economic nexus exposure must map historical sales data against each state's threshold to calculate total retroactive liability before any remediation step is taken.

Marketplace facilitator laws relieve individual sellers of sales tax collection obligations for sales made through qualifying platforms, but direct-to-consumer websites and non-qualifying channels remain the seller's independent responsibility. Some states impose nexus based on the use of third-party warehouses or fulfillment centers located in-state, even when the seller has no employees or owned property there. Affiliate nexus rules in certain states treat referral relationships or click-through arrangements as sufficient to establish a taxable presence.

A business that disagrees with a state audit assessment may file a formal administrative appeal with the state's tax tribunal or board of review within thirty to ninety days of the assessment notice, depending on the state. State tax counsel preparing an appeal must identify legal errors in the nexus determination, challenge the auditor's sampling methodology, and present documentation that reduces the assessed amount. Administrative hearings in state tax matters are formal proceedings where the quality of legal representation directly affects the financial outcome.

Most states authorize abatement of accuracy-related penalties when a taxpayer demonstrates reasonable cause for the noncompliance and good-faith reliance on professional advice. First-time penalty abatement relief is available in many states for taxpayers with a clean compliance history who promptly pay the assessed tax once notified. Tax audits and adjustments counsel can structure both the audit response and the penalty abatement request in a coordinated manner to minimize total financial exposure.

The 2018 Wayfair ruling overturned the physical presence rule, holding that South Dakota's economic nexus statute satisfied the Commerce Clause because it applied only above a minimum threshold and did not discriminate against interstate commerce. The decision also accelerated state adoption of income tax economic nexus standards, meaning a remote business can owe both sales tax and income tax to a state based solely on the volume of its in-state revenue. E-commerce sellers that crossed state revenue thresholds before registering may face multi-year retroactive assessments that significantly exceed the annual tax owed.

A remote employee who works from home in a state where the employer has no office creates physical nexus in that state based solely on the employee's presence. Most states treat a remote worker as an in-state agent of the employer, sufficient to establish both sales tax and income tax filing obligations for the company. Business tax counsel must also evaluate whether each remote employee's job duties fall outside the limited protection of P.L. 86-272, which shields only solicitation-based activities from state income tax.

Most state VDA programs limit the lookback period to three or four years, eliminating tax liability that arose before the disclosure date regardless of how long the noncompliance actually continued. The VDA agreement also typically includes a full civil penalty waiver, though interest on back taxes owed during the lookback period is usually not forgiven. Sales tax delinquency resolved through a VDA also protects a company from successor liability claims that could otherwise attach to acquirers in a future business sale.

Many states permit an initial anonymous VDA inquiry, allowing counsel to discuss the company's situation with state tax authorities on a no-name basis before any formal commitment is made. Not all states permit anonymous negotiations, and some exclude businesses that have already received audit notices or contact from the Department of Revenue. Tax debt relief counsel must confirm each state's VDA eligibility rules before beginning any outreach on behalf of a client considering voluntary disclosure.

States using a single sales factor formula assign all weight to the in-state share of total sales, while states retaining a three-factor formula weight property, payroll, and sales equally. Inconsistent sourcing rules between states, particularly for service receipts and intangibles, can result in the same revenue being sourced to two or more states simultaneously. Counsel must identify these sourcing conflicts and assert filing positions that eliminate duplicative taxation through careful allocation of receipts.

Each state maintains its own definition of taxable income, its own starting point for the calculation, and its own set of additions and subtractions from the federal base, creating compliance obligations that vary materially across jurisdictions. An annual compliance audit of the company's multi-state filing positions identifies refund opportunities, corrects errors, and reduces the likelihood of a state-initiated examination. State tax litigation attorneys who understand the procedural and substantive law of each active jurisdiction provide the most reliable protection against the compounding financial risk of multi-state noncompliance.