Since the Wayfair decision, you owe sales tax wherever your customers are — physical presence stopped being the test years ago. What's changed recently is the thresholds themselves, and sellers who set up their compliance in 2021 are often out of date without knowing it.
Economic nexus in 2026: the $100,000 rule, minus the transaction counts
Most states set economic nexus at $100,000 in annual sales into the state (California, Texas, and New York sit higher, at $500,000). The bigger shift: the majority of states have now dropped the old "200 transactions" trigger, so a seller doing 300 small orders totaling $8,000 in a state generally no longer has nexus there. If you registered in states years ago purely because of transaction counts, you may be filing returns you no longer owe — and each unnecessary registration is ongoing filing cost and audit surface.
Amazon sellers: the marketplace collects, but you're not done
Marketplace facilitator laws in every sales-tax state make Amazon collect and remit on your marketplace sales. Two traps remain. First, FBA inventory creates physical nexus: your stock sitting in a fulfillment center in Kentucky is presence in Kentucky, and several states still expect you to register even when Amazon remits the tax. Second, marketplace sales usually count toward your economic nexus thresholds — so $80,000 on Amazon plus $30,000 on your Shopify store can put you over $100,000 in a state, making the Shopify portion taxable and unremitted.
Shopify sellers: nobody is remitting for you
This is the misunderstanding that generates the ugliest back-tax bills. Shopify will calculate and collect tax at checkout if you configure it — but it never registers you and never files a return. Sellers collect tax for two years, assume it's handled, and the money sits in their bank account as an unremitted liability accruing penalties. Collected-but-not-remitted tax is treated far more harshly than tax never collected: states view it as their money that you're holding.
What non-compliance actually costs
There is no statute of limitations if you never filed. A seller who crossed nexus in Georgia three years ago owes three years of tax — out of pocket, since it wasn't collected from customers — plus penalties commonly reaching 25% and interest on top. On $400,000 of Georgia sales at roughly 8%, that's a $32,000 base liability before penalties. Most states offer voluntary disclosure agreements that cap lookback at 3–4 years and waive penalties, but only if you come forward before they find you.
The compliance sequence that works
- Run a nexus study: pull sales by state (marketplace and direct separately) for the trailing 12 months and flag every state over threshold.
- Quantify exposure in flagged states before registering — registration date questions on the application will surface your history.
- Use voluntary disclosure where back exposure is significant; register prospectively where it isn't.
- Turn on collection in Shopify only after you're registered — collecting unregistered is its own violation in some states.
- Automate filings with Avalara, TaxJar, or Numeral once you're past 4–5 states; manual filing stops scaling fast.
- Re-run the nexus study every 6 months. Thresholds are trailing, so you can cross one mid-year.
Sales tax is unforgiving but entirely mechanical. Know where you have nexus, register, collect, remit, repeat. The sellers who get hurt are the ones who never look.