US Sales Tax Nexus Guides

Four pillar guides that explain the rules the rest of this site applies state by state: what nexus is, the Supreme Court decision that created the modern threshold rule, when a marketplace collects on your behalf, and the practical registration-and-filing sequence for e-commerce sellers.

• Sales Tax Nexus Explained

  What sales tax nexus is, how the 2018 Wayfair decision reshaped it, and when remote sellers must register and collect across state lines.

  Last reviewed 2026-05-29

• Wayfair Decision & Its Impact on Sales Tax

  How the 2018 Supreme Court ruling in South Dakota v. Wayfair changed US sales tax forever, and what it means for modern remote sellers.

  Last reviewed 2026-04-23

• Marketplace Facilitator Laws

  Which marketplaces collect sales tax on your behalf, how it affects your state registrations, and when you still need to file returns.

  Last reviewed 2026-07-17

• Getting Started with Sales Tax for E-commerce

  A practical guide for e-commerce sellers (Shopify, Amazon, WooCommerce, BigCommerce) on registering, collecting, and filing US sales tax.

  Last reviewed 2026-05-11

Looking for a specific state instead? Browse all 50 state nexus pages, check the 2026 threshold and rate table, or run your numbers through the nexus calculator. How we source and review every figure is described in our methodology.