Amazon FBA Sales Tax Nexus Explained: What Sellers Actually Owe

What "nexus" actually means

Nexus is just the legal word for connection. If your business has a strong enough tie to a state, that state gets to require you to register, collect sales tax, and file returns there. That's the whole concept once you strip away the jargon. The hard part is that every state gets to define "strong enough" on its own terms, and the definitions don't line up.

For decades the only test that mattered was physical presence, an office, an employee, a warehouse full of your product. Then the 2018 Wayfair Supreme Court decision opened the door to economic nexus, which lets a state tax you based purely on sales volume or transaction count in that state, even if you've never set foot there. So today you can trip nexus two separate ways, by doing enough business in a state or by having a physical footprint in it. Most FBA sellers who get blindsided get blindsided by the second one, not the first.

The reason physical nexus catches people off guard is that it doesn't scale with your actual sales. Economic nexus at least has a logic to it, sell enough in a state and you've clearly built a real business presence there. Physical nexus from inventory storage has no such logic. A brand new product with one unit sitting in a warehouse in a state you've never shipped a single order to is, technically, enough to create a registration obligation. Most sellers' mental model of "how much business do I need to do somewhere before it counts" simply doesn't apply once inventory storage is the trigger.

That's roughly how many distinct sales tax jurisdictions exist in the US, spread across cities, counties, and states, each running its own rates and its own rules on top of the state-level framework. It's why threads about this topic on r/smallbusiness, r/tax, and r/ecommerce tend to run long and still end in disagreement. Nobody has the full 12,000-jurisdiction picture memorized, including most of the accountants posting in those threads, which is exactly why generic forum advice is a bad substitute for checking your own facts state by state.

Why FBA inventory storage is the trigger, not just having customers

Here's the part that catches sellers off guard. Having customers in a state, even a lot of them, doesn't automatically create nexus on its own, that's governed by the economic thresholds mentioned above. But physically storing inventory in a state creates nexus immediately, on day one, regardless of how many or how few units actually sell there. A single pallet sitting in a warehouse is enough. There's no minimum sales volume that has to be crossed first.

Amazon's fulfillment network is what turns this from a theoretical risk into a real one. When you enroll in FBA, you're not choosing which warehouses your stock lands in. Amazon distributes inventory across its fulfillment centers based on its own logistics and demand forecasting, and it can, and does, move your units between states without asking you first. You might ship a single shipment to one distribution center and find out months later that Amazon redistributed portions of it to five other states you never selected. Every one of those states is now a state where you may have nexus, whether you knew your inventory was there or not.

This is the mechanism that makes FBA sales tax exposure different from running your own warehouse or a single 3PL. You have far less control over where your physical presence actually exists, and that lack of control doesn't excuse you from the resulting obligations. States don't care that Amazon made the routing decision. If your product sat in their state, the nexus question is on the table.

How to actually find out where your inventory is sitting

You can't assess your exposure if you don't know where your stock has been. Seller Central has the data, it's just not sitting on the dashboard waiting for you. The two reports worth knowing are the Inventory Event Detail Report and the cross-border inventory reports available to sellers enrolled in multi-country or multi-warehouse programs.

• Inventory Event Detail Report. Found under Reports, then Fulfillment. This gives you a granular, event-by-event log of inventory movement, including receipts, transfers between fulfillment centers, and removals, so you can reconstruct which states your units actually touched over a given period rather than guessing.
• Inventory ledger and storage fee reports. These summarize where your inventory sat at the end of each period, which is a faster way to spot states with meaningful storage duration versus states where a handful of units passed through briefly.
• Cross-border and Pan-EU inventory reports. If you're enrolled in a program like Pan-European FBA or a similar cross-border inventory placement service, these reports are essential since Amazon actively redistributes stock across country borders as part of the program's normal operation, not as an edge case.

Pull these quarterly at minimum if you're running any real volume through FBA. A once-a-year check means you could be sitting on unaddressed nexus in a state for the better part of a year before you even notice the exposure exists.

When you pull these reports for the first time, expect the list of states to be longer than you assumed. Sellers who picture their FBA footprint as "wherever I sent my last shipment" are usually surprised to see a dozen or more states show up once transfers, returns processing, and redistribution are all accounted for. Build a simple running log, state, first date inventory appeared, whether you've confirmed nexus and registered, so the next quarterly pull is a comparison against your existing record instead of starting the whole exercise from zero every time.

What marketplace facilitator laws actually cover

The good news, and it's real good news, is that marketplace facilitator laws are now active in every US state that has a sales tax. Under these laws, Amazon itself calculates, collects, and remits sales tax on your marketplace sales directly to the state, on your behalf, automatically. You don't have to configure this per state or per transaction. It happens in the background on every qualifying sale.

This genuinely solved the biggest headache sellers used to face, which was manually collecting and remitting tax across dozens of jurisdictions with different rates and filing calendars. For pure marketplace sales through Amazon, that burden has effectively moved to Amazon. It's one of the rare instances where a platform absorbed real operational complexity on sellers' behalf rather than pushing it downstream.

What's still your responsibility even with Amazon collecting

Several states require a business with nexus to register for a sales tax permit and maintain that registration even when all of the actual tax collection is being handled by a marketplace facilitator. Some states also require periodic informational filings, essentially a return that reports zero tax due because Amazon already remitted it, just to keep your registration current and demonstrate compliance. Skipping these because "Amazon's already paying it" is a common and avoidable mistake.

And critically, marketplace facilitator laws only apply to marketplace sales. If you sell the same products through your own Shopify store, through a wholesale channel, through a different marketplace that doesn't have facilitator coverage in a given state, or at trade shows, none of that revenue is covered by Amazon's collection on your behalf. If you have nexus in a state from FBA inventory storage, that nexus applies to all of your sales activity in that state, not just the portion that happens to run through Amazon. A lot of sellers only discover this distinction when a state audit letter shows up asking about non-Amazon revenue they assumed was covered.

If you realize you have unaddressed nexus, here's how to fix it

First, don't panic and don't ignore it either. Both reactions make the eventual cost worse. Start by getting an accurate picture using the inventory reports above, covering as far back as your records reasonably allow, so you know which states and roughly which time periods are actually in play.

It's worth saying plainly that doing nothing is the worst of the available options, not a neutral one. Unregistered nexus doesn't expire or become less relevant with time, if anything the opposite, since any eventual back-tax calculation typically covers the full period you had nexus and weren't registered, plus interest. States aren't chasing every small seller with FBA inventory, but they do run data-matching programs against Amazon's own records, and the risk compounds the longer it sits unaddressed rather than staying flat.

1. Confirm nexus state by state. Cross-reference your inventory storage history against each state's specific nexus rules and registration thresholds. Some states have de minimis carve-outs even for physical presence, most don't.
2. Register going forward before you fix the past. Getting current registration in place stops the exposure from growing while you work out what, if anything, is owed retroactively.
3. Look into voluntary disclosure agreements. Most states offer a VDA program that limits how far back they'll look and often waives penalties, in exchange for you coming forward before they find you first. This is usually far cheaper than waiting for an audit.
4. Reconstruct historical liability carefully. Even where Amazon was collecting tax on marketplace sales, you need to confirm that coverage actually applied for the full period in question, since facilitator law effective dates vary by state and weren't all simultaneous.

When it's time to bring in a sales tax professional

If you're a small seller with inventory sitting in one or two states and modest volume, you can often handle registration and any informational filings yourself once you understand the requirements. Seller Central's reports plus a state's own registration portal are usually enough.

Once you're storing inventory across a handful of states, especially through a cross-border program that actively redistributes stock, or once you discover a multi-year gap in registration, it's worth paying for actual expertise. A sales tax professional or a dedicated service can run a full nexus study across your historical inventory data, handle voluntary disclosure negotiations with multiple states simultaneously, and set up ongoing monitoring so you're not doing this forensic exercise again in another two years. The cost of getting this wrong, back taxes, penalties, and interest compounding across multiple jurisdictions, tends to dwarf the cost of a few hours of professional time spent getting it right upfront.

There's also a practical signal worth watching for beyond raw state count, how much of your product mix is genuinely stable versus how often you're launching new SKUs or entering new categories. Sellers with a static catalog can often keep the nexus picture manageable with a periodic in-house review. Sellers who are constantly launching new products, and therefore constantly generating new inventory placement events across the fulfillment network, tend to outgrow the do-it-yourself approach faster than they expect, simply because the compliance surface area keeps expanding underneath them.