Do online sellers have to collect sales tax in every state they ship to? It depends on where a seller has established 'nexus' — a legal connection to a state significant enough to require tax collection — which today can be triggered by sales volume alone, not just a physical presence. In practice, marketplaces like Amazon or Etsy often collect and remit sales tax automatically on a seller's behalf, but sellers running their own storefront need to track economic nexus thresholds state by state.

Article Summary

  • Since a landmark Supreme Court ruling changed the rules, physical presence in a state is no longer required to owe sales tax there — crossing a sales or transaction threshold can create that obligation on its own.
  • Marketplace facilitator laws now shift much of the sales tax collection burden onto platforms like Amazon and Etsy, but sellers using their own website generally still must handle it themselves.
  • Income tax and sales tax are entirely separate obligations — collecting and remitting sales tax correctly says nothing about whether income tax has been accurately reported on the resulting profit.

"Time is your friend; impulse is your enemy."

John Bogle

An ecommerce seller shipping orders to all fifty states can feel, at a glance, like they're simply running one shop. Legally, they may be operating in dozens of different tax jurisdictions at once, each with its own rules about when a seller owes sales tax and when a marketplace has already handled it for them. The rules changed meaningfully in recent years — physical presence used to be the deciding factor, and now sales volume alone can trigger an obligation. Sellers who scaled quickly, especially those running their own storefront outside a marketplace, are the ones most likely to discover this gap the hard way.

What 'Nexus' Means and Why It Changed

'Nexus' is the legal term for a connection to a state significant enough that the state can require you to collect and remit its sales tax. For decades, nexus generally required physical presence — an office, a warehouse, an employee — in that state. A landmark Supreme Court decision changed that by allowing states to establish 'economic nexus' based on sales volume or transaction count alone, meaning a seller with no physical presence in a state can still owe sales tax there once they cross that state's specific threshold. Because these thresholds and rules vary by state and can change, sellers with meaningful volume shipping across many states generally need either sales tax automation software or a professional to track which states they've crossed into, rather than trying to monitor dozens of separate state rules manually.

Marketplace Facilitator Laws: Who Actually Collects the Tax

Most states have adopted 'marketplace facilitator' laws that shift the responsibility for collecting and remitting sales tax onto large marketplaces like Amazon, Etsy, or eBay, rather than the individual seller. In practice, this means a seller operating exclusively through such a marketplace often has sales tax handled automatically behind the scenes on marketplace orders. That protection generally does not extend to sales made through a seller's own website, a separate Shopify store, or in-person sales at markets and pop-ups — those channels typically remain the seller's own responsibility to track and remit. This creates a common blind spot for sellers who run a hybrid business: comfortable that 'sales tax is handled' because their marketplace sales are covered, while direct sales through their own site quietly accumulate an unaddressed obligation in states where they've crossed the economic nexus threshold.

Income Tax and Inventory: The Separate Track

Sales tax and income tax are entirely different obligations that sellers sometimes conflate. Collecting sales tax from a customer and remitting it to a state has nothing to do with reporting your own business profit for income tax purposes — that money was never yours to begin with, it was collected on the state's behalf. Separately, ecommerce sellers need to track cost of goods sold accurately, since inventory purchased but not yet sold generally isn't deductible until it's actually sold, which differs from simply deducting every purchase the moment it's made. Sellers who don't track inventory carefully can end up overstating expenses in a purchasing-heavy month and understating profit, only to have the picture reverse once that inventory sells through in a later period. Consistent, itemized bookkeeping — separating sales tax collected, cost of goods sold, platform fees, and shipping costs — is what makes an accurate income tax return possible at year-end.

A Practical Framework for Staying Compliant

Identify every channel you sell through and separately check whether each one qualifies as a marketplace facilitator handling sales tax on your behalf, since the obligation differs meaningfully between a marketplace listing and your own storefront. For any channel where the responsibility falls on you, use sales tax automation software to monitor your transaction volume and dollar thresholds by state, since manually tracking dozens of state rules is unrealistic once volume grows. Keep sales tax collected in a separate ledger line from revenue, since it was never your income to begin with. Track cost of goods sold and inventory purchases distinctly from other business expenses so your income tax return reflects actual profit rather than raw cash outflow. When your footprint expands to several new states or a new sales channel, revisit your nexus exposure rather than assuming last year's setup still covers this year's business.