How Sales Tax Nexus Works for Online Sellers

How Sales Tax Nexus Works for Online Sellers

Sales tax nexus is a connection between your business and a state that is strong enough to require you to collect and remit that state's sales tax. For online sellers, nexus can come from a physical presence like inventory or employees, or purely from economic activity, exceeding a state's sales threshold. Here is how nexus works, what creates it, and what to do when it applies to you.

This is the concept that catches online sellers off guard, because it means you can owe sales tax obligations in states you have never visited. Rules vary by state and change often, so treat this as a map, not a substitute for checking each state's current rules.

What Nexus Means

Nexus is simply the legal threshold at which a state can require your business to collect its sales tax. Cross that threshold and you generally must register with the state, collect the right amount of tax from customers there, and remit it on a schedule. Below it, you generally have no such obligation in that state.

For decades, nexus required a physical presence. That changed in 2018.

Physical Nexus

A physical presence in a state still creates nexus. For online sellers, this commonly shows up as:

• An office, store, or warehouse in the state.
• Employees or, in some cases, contractors located there.
• Inventory stored in the state, including in a marketplace's fulfillment warehouse. This one surprises many sellers, because your goods can sit in a state you have never set foot in.

Economic Nexus After Wayfair

The 2018 South Dakota v. Wayfair decision allowed states to base nexus on economic activity alone. Now most states impose economic nexus once your sales into the state exceed a threshold, commonly defined by a dollar amount of sales, a number of transactions, or both, within a period. Exceed it, and you generally must register and collect, even with no physical presence.

Thresholds and definitions vary by state, so the same sales volume can create nexus in one state and not another. This is the change that turned sales tax into a multistate puzzle for online sellers.

Marketplace Facilitator Rules

Many states now require marketplaces like Amazon to collect and remit sales tax on sales made through their platform. That helps, but it does not always cover everything: sales through your own website or other channels may still create obligations, and you may still need to register or file in some states. Do not assume the marketplace handles all of it.

What to Do When Nexus Applies

When you suspect you have nexus in a state, the usual steps are to confirm the state's current threshold, determine when you crossed it, register with the state if required, begin collecting the correct tax going forward, and assess any past liability. Ignoring it does not make it go away; unpaid sales tax can accrue with interest and penalties.

Because tracking thresholds across many states is genuinely complex, this is where an ecommerce specialist adds value. ECOM CPA is a Sam's List firm focused on ecommerce sellers, including the multistate sales tax mapping and registration that comes with selling everywhere at once. Confirm credentials and fit before engaging.

Frequently Asked Questions

What is sales tax nexus in simple terms? Nexus is a connection between your business and a state strong enough to require you to collect and remit that state's sales tax. It can come from a physical presence, like inventory or employees, or from economic activity, like exceeding the state's sales threshold after the 2018 Wayfair decision.

Does storing inventory in a state create sales tax nexus? Often yes. Inventory stored in a state, including in a marketplace fulfillment warehouse, can create physical nexus there even if you have never visited. Sellers using fulfillment services should know which states hold their inventory, since it can create collection obligations they did not expect.

If Amazon collects sales tax, am I fully covered? Not necessarily. Marketplace facilitator laws require platforms like Amazon to collect on sales through them, but that may not cover sales on your own website or other channels, and you may still have registration or filing duties in some states. Confirm your full obligations rather than assuming the marketplace handles everything.

How do I figure out where I owe sales tax? Compare each state's current economic nexus threshold against your sales and transactions there, and account for physical connections like inventory or employees. Because thresholds and rules vary and change, many sellers use a specialist to map their nexus footprint and handle registration and filing.