Quick overview

Business nexus determines whether a state has the legal authority to tax your company. After the 2018 U.S. Supreme Court decision in South Dakota v. Wayfair, Inc., states can — and many do — apply “economic nexus” rules based on sales or transaction thresholds, not just physical presence. That change is central to how modern multi‑state tax compliance works (South Dakota v. Wayfair, Inc., 2018).

Legal background and why Wayfair matters

Until the Wayfair decision, the leading test for state taxing power came from Quill Corp. v. North Dakota, which required a physical presence in the taxing state. Wayfair overturned that bright‑line physical presence rule for sales tax and allowed states to adopt economic‑nexus standards tied to in‑state sales or transaction counts. Since 2018, most states have followed suit with economic thresholds and new rules for remote sellers, marketplace facilitators, and digital businesses.

Note: Wayfair relates primarily to state sales and use tax collection. States also use nexus concepts for income tax, franchise tax, and payroll withholding; rules vary by tax type and by state. For an in‑depth look at the sales tax implications for remote sellers, see FinHelp’s guide on Multi‑State Sales Tax Nexus: Rules for Remote Sellers.

Common types of nexus

  • Physical presence nexus: traditional triggers such as an office, retail location, warehouse, inventory in a third‑party fulfillment center (e.g., Amazon FBA), or employees working in a state.
  • Economic nexus: based on dollar sales or number of transactions into the state. States commonly set thresholds (examples include $100,000 in sales or 200 transactions, but the exact test varies by state and tax type).
  • Click‑through / affiliate nexus: having affiliates, referral arrangements, or significant online relationships that create a taxable connection under some states’ statutes.
  • Marketplace facilitator rules: platforms like Amazon, Etsy, or eBay may be required to collect and remit sales tax on behalf of sellers in many states.
  • Employee and payroll nexus: having remote employees can create withholding obligations and may also create income tax nexus for the business.

Each state writes its own statutes and regulations, so the presence or absence of a particular trigger depends on that state’s law. For practical compliance steps when selling nationwide, see FinHelp’s article on How to Maintain Sales Tax Compliance When Selling Online Nationwide.

How states apply nexus across tax types

  • Sales and use tax: States often enforce economic nexus for remote sales (post‑Wayfair). Many also require marketplace facilitators to collect tax. States publish the specific thresholds on agency websites.
  • Income and franchise taxes: States use nexus and apportionment rules to determine if a company must file a corporate or pass‑through return. Factors include payroll, property, and sales in the state.
  • Payroll and withholding: Employees working from a state typically trigger withholding and unemployment insurance obligations for employers.

Because the tests differ by tax type, businesses must evaluate nexus separately for sales tax, income/franchise tax, and payroll obligations.

Practical steps to determine whether you have nexus

  1. Inventory your footprint: List physical locations, employees, contractors, inventory in third‑party warehouses, sales channels, and affiliate relationships.
  2. Track sales and transactions by state: Use your accounting system or sales platform to produce state‑level revenue and transaction counts. Many nexus tests are based on calendar year totals.
  3. Review state thresholds and statutes: Check each state’s department of revenue website for the latest economic nexus thresholds and guidance (these change frequently). The Tax Foundation and state pages are helpful references.
  4. Evaluate marketplace facilitator rules: If you sell through marketplaces, determine whether the marketplace or you are responsible for collection.
  5. Consider income tax and payroll: Determine whether employees or contractors create withholding or income tax filing obligations.
  6. Get advice for complex situations: Nexus audits and multi‑state apportionment can be complicated; consult a state tax specialist for large or high‑risk exposures.

Real‑world examples and common traps

  • Example 1 — Remote seller who hit a threshold: An online retailer headquartered in State A made $125,000 in sales to customers across State B in one calendar year. If State B’s economic‑nexus threshold is $100,000, the retailer must register, collect sales tax from customers in State B, and file returns there. Failing to register can lead to assessments, penalties, and interest.

  • Example 2 — Fulfillment by a third party: Many sellers don’t realize that storing inventory in a third‑party warehouse inside State C (for faster shipping) can create physical presence nexus in State C.

  • Example 3 — Remote employees: A SaaS company with a salesperson who works from a home office in State D may trigger income tax filing and withholding obligations in State D, even if the company never had an office there.

Common mistakes include assuming physical presence is required, ignoring marketplace rules, or failing to track transaction counts and in‑state sales.

Registration, collection, and filing: what to expect

  • Registration: If you determine you have nexus, register with the state’s department of revenue for the relevant tax types (sales tax permit, withholding account, or corporate registration).
  • Collection: Once registered for sales tax, you must collect the correct tax rate from customers at the point of sale. Rates may include state, county, and local components.
  • Filing and remittance: File returns on the required cadence (monthly, quarterly, or annually) and remit collected taxes. If you missed past obligations, the state may pursue back taxes and penalties; voluntary disclosure agreements can sometimes limit penalties.

Keep in mind that local tax rates, special district taxes, and sourcing rules can complicate calculations. Sales tax automation tools can reduce errors and administrative burden—see our guide on How to Implement Sales Tax Automation for Small Businesses.

Audit risk, penalties, and mitigation

  • Audit triggers: Rapid growth, sudden use of third‑party fulfillment, registration gaps, or large sales into a previously unregistered state increase audit risk.
  • Common penalties: States can assess unpaid tax, interest, and penalties for late registration or nonpayment. Penalty relief may be available for voluntary disclosure and prompt correction.
  • Mitigation strategies: Regularly reconcile state sales activity, maintain clear records, register proactively when thresholds are approached or exceeded, and maintain written nexus policies.

Recordkeeping and technology

Good records make a nexus audit manageable. Keep sales by state, nexus analyses, employee location records, contracts with affiliates and marketplaces, and shipping documentation. Tax engines and accounting systems that tag transactions by destination state reduce manual work and improve accuracy.

Tips from practice

  • Start early: It’s easier and cheaper to register and collect tax as thresholds are approached than to fix problems after an audit.
  • Use a test environment: Before rolling out tax collection changes, test with a sandbox to confirm rates apply correctly by ZIP code.
  • Beware marketplace assumptions: Don’t rely solely on the marketplace to handle all compliance—review each marketplace’s remittance policy for the states where you have sales.
  • Document decisions: Keep a dated record of nexus evaluations and the factual basis for registrations or nonregistrations.

Where to confirm rules and get help

  • Read the state department of revenue guidance where you suspect nexus; these are the final authority for state rules.
  • Review Supreme Court guidance in South Dakota v. Wayfair, Inc. (2018) for the legal foundation of modern economic nexus.
  • Consult a qualified state tax advisor for analyses involving significant revenue, multi‑state payroll, or complex apportionment issues.

Authoritative sources: South Dakota v. Wayfair, Inc. (2018); state department of revenue websites; Tax Foundation analyses on economic nexus and marketplace facilitator rules.

Professional disclaimer

This article is educational and not tax or legal advice. Nexus analysis depends on facts and state law; consult a licensed tax professional or attorney before making compliance decisions.