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Sales Tax Nexus for Ecommerce Sellers (2026)

A cautious, educational overview of what sales tax nexus means for online sellers — physical vs economic nexus, why thresholds vary by state, and why this is a use-a-specialist-tool topic.

By Marginory team · Online sellers with hands-on experience across Etsy, Shopify & PODUpdated Fee data verified against official platform documentation

Not tax or legal advice — read carefully. Sales tax nexus is one of the most fact-specific and state-variable topics in ecommerce compliance. This page explains general concepts only. It does not tell you where you currently owe sales tax, and getting this wrong has real financial consequences (back taxes, penalties, interest). Marginory is not a tax, accounting, or law firm. Use a dedicated sales tax compliance tool or a licensed CPA/sales tax attorney for your actual obligations.

Two kinds of nexus

Physical nexusexists when your business has a tangible presence in a state — an office, a warehouse, an employee or contractor working there, or inventory physically stored there. This last point matters a lot for ecommerce sellers: storing inventory in a third-party fulfillment warehouse (including FBA-style networks that distribute inventory across multiple states) is commonly cited as something that can create physical nexus in states you've never personally visited.

Economic nexusexists when your sales activity into a state is significant enough — regardless of physical presence — to trigger a collection requirement. This concept became possible nationwide after the Supreme Court's 2018 decision in South Dakota v. Wayfair, which allowed states to require out-of-state sellers to collect sales tax based on sales volume alone.

The $100,000 / 200-transaction threshold — common, not universal

Many states modeled their economic nexus threshold on South Dakota's original law: roughly $100,000 in sales, or 200 separate transactions, into the state in a year. It's useful as a mental starting point — but it is nota single national rule. Some states use different dollar thresholds, some have dropped the transaction-count leg entirely (keeping only the dollar threshold), some measure over a different time period, and the numbers can change as states update their laws. Never assume a specific state uses exactly $100,000/200 without checking that state's current statute or a compliance tool that tracks it.

Why this is a "use a tool or a specialist" topic

Tracking nexus manually across up to 45 states with a sales tax (most states plus DC currently impose one) means monitoring rolling sales totals, transaction counts, and threshold rules that each state can change independently. Sellers who've crossed — or are approaching — an economic nexus threshold in more than a state or two typically use a dedicated sales tax automation platform (TaxJar, Avalara, and similar tools track thresholds, calculate rates, and help file returns) rather than attempting it by hand. Below that scale, a CPA experienced in multi-state ecommerce can advise on your specific footprint.

What to do next

  • List every state where you have physical presence, including any state where a fulfillment network stores your inventory.
  • Track your rolling 12-month sales dollars and transaction count by state — most sales tax automation tools will do this for you automatically.
  • Before assuming you're under a threshold anywhere, verify that state's current economic nexus rule directly — thresholds and rules change.
  • If you're unsure whether you've triggered nexus anywhere, that uncertainty itself is a good reason to consult a sales tax specialist rather than guess.
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Frequently Asked Questions

Is this page tax or legal advice?
No, and this topic in particular deserves extra caution: sales tax nexus rules genuinely differ across all 50 states, change over time, and carry real financial consequences if gotten wrong. This page is a general educational overview of the concepts involved, not a determination of where you owe sales tax. Marginory is not a tax, accounting, or law firm. Use a dedicated sales tax compliance tool (such as TaxJar or Avalara) or consult a CPA or sales tax attorney for your actual filing obligations.
What is sales tax nexus, in plain terms?
Nexus is the legal connection between your business and a state that's strong enough for that state to require you to collect and remit its sales tax. There are two broad kinds: physical nexus (a tangible presence in the state — an office, warehouse, employee, or inventory stored there) and economic nexus (enough sales activity into the state, even with zero physical presence, to trigger the requirement).
Is the $100,000/200-transaction threshold the law in every state?
No — it's a common reference point, not a uniform national rule. Following the 2018 South Dakota v. Wayfair Supreme Court decision, many states adopted economic nexus thresholds resembling $100,000 in sales or 200 transactions in a year, but the exact dollar amount, transaction count (some states have since dropped the transaction-count leg entirely), and measurement period vary by state and change over time. Treat $100,000/200 as a starting point for research, never as a confirmed number for a specific state without checking that state's current rule.
Does storing inventory in a fulfillment warehouse create nexus?
Storing inventory in a state — including inventory held in a third-party fulfillment center, such as an FBA warehouse — is a commonly cited example of what can create physical nexus in that state, even if you never set foot there yourself. This is a frequently misunderstood point for sellers using fulfillment networks, and it's exactly the kind of fact-specific question a sales tax specialist should confirm for your actual fulfillment footprint.
How do most sellers actually handle multi-state sales tax compliance?
Most sellers past a certain sales volume use a dedicated sales tax automation tool (such as TaxJar or Avalara) that tracks nexus thresholds across all states, calculates the correct rate at checkout, and helps file returns — rather than trying to track 50 states' worth of rules manually. Below a certain size, a CPA familiar with multi-state ecommerce sales tax can advise on whether registration is currently needed anywhere. This is not a do-it-yourself-with-a-spreadsheet topic once you're selling into more than a couple of states.