Overview

State nexus decides whether a state can impose sales-tax duties on a marketplace, platform, or the sellers using it. The U.S. Supreme Court’s 2018 decision in South Dakota v. Wayfair, Inc. removed the strict physical‑presence rule and opened the door for economic nexus standards; since then most states have adopted thresholds that can trigger tax obligations (see South Dakota v. Wayfair, Inc., 138 S. Ct. 2080 (2018)). For a plain‑language primer from the IRS on nexus concepts, see the IRS nexus overview (IRS).

Common nexus triggers for marketplaces and platforms

  • Physical presence: offices, employees, inventory, or fulfillment centers located in a state.
  • Economic presence: meeting a state’s sales threshold—many states use thresholds such as $100,000 in sales or 200 transactions, but amounts differ by state and can change.
  • Marketplace‑facilitator laws: many states require the marketplace to collect and remit tax on behalf of third‑party sellers. See FinHelp’s guide to Understanding State Sales Tax on Marketplace Facilitators.
  • Affiliate or click‑through nexus: relationships with in‑state partners or referral arrangements that create a connection.
  • Digital goods and subscriptions: some states tax digital products and SaaS; rules are state‑specific — see our Sales Tax Compliance for Digital Goods: Best Practices.

Who is affected

  • Marketplaces that list third‑party sellers (e.g., platforms similar to Etsy or app stores).
  • Platforms that facilitate payment, fulfillment, or provide merchant services.
  • Independent sellers who use marketplaces—nexus may shift collection duties to the marketplace but can still create registration and reporting needs for sellers.

Practical compliance steps (actionable checklist)

  1. Map your activities by state: inventory locations, employees, contractors, marketing, and fulfillment partners.
  2. Monitor sales by state continuously: implement a dashboard that tracks gross sales and transaction counts by destination.
  3. Confirm marketplace‑facilitator statutes: if your platform meets the state’s definition, you may be responsible for collection and remittance. For details, consult state revenue sites and our internal guide on marketplace facilitators.
  4. Register and obtain sales‑tax permits promptly in states where nexus exists.
  5. Implement tax‑calculation and filing software that supports multi‑jurisdiction rates, exemptions, and returns.
  6. Maintain clear records: transaction-level data, exemptions, and seller onboarding documents for 4–7 years depending on state rules.
  7. Consider voluntary disclosure agreements (VDAs) if you discover past noncompliance — VDAs often limit look‑back periods and penalties.

Marketplace‑specific nuances

  • Collection obligation vs. liability: marketplace facilitator laws often make the platform the collector, but seller exposure can remain for registration, reporting, or local taxes. Verify how each state allocates responsibility.
  • Seller onboarding: collect adequate tax‑ability information (e.g., exemption certificates) and document whether the marketplace or seller is the collecting agent.
  • Fulfillment networks (FBA/third‑party logistics): inventory stored in state warehouses can create nexus. See state guidance and our article on Multistate Sales Tax Basics for Online Sellers.

Real‑world guidance from practice

In my practice advising digital marketplaces, the most common surprise is inventory and fulfillment. A startup used a third‑party warehouse network and later received notices from several state tax authorities because inventory placed in those warehouses created nexus. Early mapping of fulfillment locations and automated tax collection prevented costly retroactive audits for other clients.

Common mistakes to avoid

  • Assuming a single threshold applies nationwide—thresholds and transaction tests vary by state.
  • Relying solely on sellers to collect tax when state law names the marketplace as the collector.
  • Poor recordkeeping for exemptions and out‑of‑state sales.

When to get professional help

If you move inventory, exceed rapid growth in a state, have many small sellers, or operate cross‑border digital subscriptions, consult a state sales‑tax specialist or CPA to confirm registration, collection, and filing obligations.

Authoritative sources and state guidance

Internal resources

Professional disclaimer

This article explains general principles about state nexus for digital marketplaces and platforms and does not replace individualized tax advice. For obligations specific to your business and states where you operate, consult a qualified tax professional or state revenue agency.