E-commerce Seller State Tax Guide: Nexus, Compliance, and Planning

Selling online used to mean you only collected sales tax in the state where your business was located. That world ended in June 2018, when the Supreme Court's decision in *South Dakota v. Wayfair* rewrote the rules for every e-commerce seller in America. Today, a seller in one state can be legally required to collect and remit sales tax in dozens of others — and failing to do so can generate crippling back-tax liabilities. This guide explains nexus, the current economic thresholds, marketplace facilitator laws, and a practical compliance strategy.

What Is Nexus?

"Nexus" is the legal connection between your business and a state that triggers a sales-tax collection obligation. There are two kinds:

Physical nexus is the traditional form: having a tangible presence in a state — an office, a warehouse, inventory, an employee, or even a contractor. If you store goods in a state (including in an Amazon fulfillment center), you almost certainly have physical nexus there.

Economic nexus is the post-*Wayfair* form: you can be required to collect tax based purely on your sales volume into a state, with no physical presence at all. Cross a state's dollar or transaction threshold and you have economic nexus.

The Wayfair Decision (2018)

Before *Wayfair*, the *Quill* precedent (1992) required physical presence before a state could force tax collection. *South Dakota v. Wayfair, Inc.* overturned *Quill*, ruling that South Dakota could require out-of-state sellers exceeding $100,000 in sales or 200 transactions to collect tax. Within two years, nearly every state with a sales tax had enacted its own economic-nexus law modeled on South Dakota's.

Economic Nexus Thresholds (2026)

Thresholds vary by state, so you must track sales into each one:

• Most states: $100,000 in sales OR 200 separate transactions
• California: $500,000 in sales (no transaction count)
• Texas: $500,000 in sales
• New York: $500,000 in sales AND more than 100 transactions
• Florida: $100,000 in sales (no transaction count)

Note the trend: several states have dropped the 200-transaction test because it unfairly caught small sellers of low-priced goods. Always check the current rule for each state — they change frequently.

Marketplace Facilitator Laws

This is the single most important development for small sellers. Nearly every state now has a marketplace facilitator law that shifts the collection duty to the platform. If you sell on Amazon, eBay, Etsy, or Walmart, the marketplace itself collects and remits sales tax on your behalf for those transactions.

That means your compliance burden is often much smaller than it first appears — but with two big caveats:

1. You may still owe tax on sales through your own website (Shopify, WooCommerce, etc.) where no facilitator is involved.

2. You may still have registration and filing obligations in states where you have nexus, even if the marketplace collects the tax. Some states require a "zero return."

A Practical Compliance Strategy

1. Track your sales by state — use your platform's reports or automation software to know where you are approaching a threshold

2. Register for a sales-tax permit in each state where you have nexus (never collect tax without a permit — that is illegal in most states)

3. Use automation — tools like Avalara or TaxJar calculate rates, track nexus, and file returns across states

4. Let marketplaces collect where they can and focus your own effort on direct-website sales

5. Consider your business formation state — Delaware, Wyoming, and Nevada offer favorable business climates, though formation state does not eliminate nexus in states where you sell

6. File on time — deadlines vary (monthly, quarterly, annually) and penalties compound quickly

Common Mistakes

• Ignoring economic nexus because "I don't have an office there" — sales volume alone creates obligations
• Collecting tax without registering — this exposes you to penalties
• Assuming Amazon covers everything — your own website sales are your responsibility
• Forgetting to file zero returns where required

Summary

Post-*Wayfair*, e-commerce sales tax is a multi-state compliance project, not an afterthought. Track your sales into every state, register where you cross a threshold, lean on marketplace facilitator laws to reduce your burden, and automate the rest. When in doubt about a specific state, consult that state's Department of Revenue or a sales-tax professional — the rules genuinely differ state by state.