Ecommerce Sales Tax: US Compliance Guide for Online Sellers

You launch an online store, sales arrive from thirty states, and nobody sends you a bill. Then a threshold trips in a state you have never visited, and it all lands at once: register here, collect at this rate, file by the twentieth, break the total down by county.

It does not have to go that way. You can know which states you already owe in and what is taxable in each. You can decide deliberately whether tax gets added at checkout or folded into your price, and you can see your filing calendar a year ahead.

Ecommerce sales tax is not a checklist, which is why checklists keep failing online sellers. It is four decisions, and each one fails differently: where you owe, what you owe it on, how you show it to the buyer, and how you file.

Sales tax nexus governs the first and product taxability governs the second. The third is the one almost nobody writes about. The fourth is where the money actually moves.

This guide takes the four decisions in the order they hit a growing online business, whether you sell through your own store, a marketplace, or both.

How ecommerce sales tax works in the US

There is no national sales tax here. Instead, 45 states and the District of Columbia levy a statewide sales tax, and inside them, counties, cities and special districts stack their own rates on top. The sales tax rate a customer pays is the sum of those layers at their delivery address.

Five states have no statewide sales tax: New Hampshire, Oregon, Montana, Alaska and Delaware.

Alaska is the trap in that list. It has no statewide rate, but more than 100 local jurisdictions collect through the Alaska Remote Seller Sales Tax Commission.

That commission applies a single statewide threshold of 100,000 dollars, and it has since dropped its transaction-count test.

So a seller who writes Alaska off because "there is no sales tax there" is wrong in a way that compounds quietly. Our Alaska sales tax guide covers how the local layer works.

The hinge for everything that follows is South Dakota v. Wayfair, decided in June 2018. Before it, a state needed your physical presence to make you collect. After it, your sales volume alone is enough, and every state with a sales tax has written that standard into law.

Two consequences follow, and together they explain why online sellers find this harder than shop owners do:

• Sales tax follows the buyer, not the seller. Almost every state sources tax to the customer's delivery address, so your own location mostly does not matter. One day of orders can span several hundred rate combinations.
• The obligation attaches without any action from you. You do not opt into a state. You cross a number, and the duty is simply there.

That second point is the whole first decision.

Decision 1: where you owe, and how sales tax nexus starts

Sales tax nexus is the connection between your business and a state that gives that state the right to make you collect. It is binary. If you have nexus in a state you collect there, and if you do not, you do not. There is no partial version.

Three kinds of sales tax nexus matter for an online business, and they are worth taking in the order they tend to bite.

Physical presence nexus

The oldest test and still the broadest. An office, a warehouse, a store, an employee, a contractor, inventory sitting in a fulfillment center, and in some states even attending a trade show. Physical presence nexus carries no threshold at all, so a single warehouse creates nexus on day one.

Third-party fulfillment is where this catches people. A marketplace moves your inventory into a local warehouse, and you acquire physical presence in that state on zero sales volume. You need never have set foot there.

Economic nexus

The Wayfair test, and the one that drops online sellers into states they have never visited. Cross a sales figure into a state and economic nexus attaches there.

Most states set the bar at 100,000 dollars in the current or previous calendar year. The outliers matter more than the norm, though, because they are the states most online businesses reach first.

Threshold	States	What to watch
100,000 dollars	The large majority, including Florida, Georgia, Washington and Illinois	Some states measure gross sales, others only taxable sales. The gap matters if much of your catalog is exempt.
250,000 dollars	Alabama, Mississippi	A higher bar, so it is easy to forget until you are well past it.
500,000 dollars	California, Texas, New York	The three biggest markets have the highest bars, which is why many sellers register in small states first.
Dollars and transactions together	New York, Connecticut	Both conditions must be true, so a high-value, low-volume seller can stay under.

The transaction count is on its way out of economic nexus laws. More than a dozen states have dropped the 200-transaction test in favor of a revenue-only sales threshold, with Illinois and Kentucky among the most recent.

That is good news for anyone selling low-priced digital goods, where 200 orders used to arrive long before any meaningful revenue did.

Two pieces of fine print do more damage than the numbers themselves:

• The measurement window usually rolls across the current and previous calendar year. You can trip an economic nexus threshold in January on the strength of last year's sales.
• Most states measure gross sales, including the orders a marketplace already collected tax on. So you can owe a registration in a state where you personally collected nothing.

We keep the state-level detail elsewhere rather than repeating it here. Our state-by-state sales tax compliance analysis has the full breakdown. The sales tax nexus definitions guide covers click-through, affiliate and cookie nexus, which still exist in a handful of states.

Marketplace nexus

Sell through Amazon, eBay, Etsy or Walmart, and marketplace facilitator laws hand the sales tax collection duty to the platform. Every state with a sales tax now has them on the books. The marketplace calculates, collects and remits on those orders, and you do not file them.

Marketplace nexus is the single biggest relief valve in US ecommerce sales tax, and also the most misread. Three things marketplace facilitator laws do not do:

• They do not exempt your own store. Orders through your own checkout remain entirely yours.
• They do not remove your registration duty. Most states still count facilitated sales toward your economic nexus threshold, and several want them reported as exempt sales even though the platform paid the tax.
• They do not cover every product or channel. Coverage varies, and a company that only processes payments is not automatically a facilitator.

Our guide to US marketplace facilitator laws works through where the line falls.

How to work out where you already have nexus

Most online sellers discover nexus retroactively, which is the expensive way to find out. The determination itself is arithmetic you can finish in an afternoon.

Start with a sales-by-state report covering the last two calendar years, pulled from every channel you sell through and combined into a single figure per state. Then, state by state, answer three questions:

• Does the combined figure cross that state's economic nexus threshold, in either the current or the previous calendar year? Most states test both windows, so clearing one is not enough.
• Does the state measure gross sales or only taxable sales, and does it count marketplace-facilitated orders? Those two answers change the number you are comparing against the threshold.
• Is there any physical presence? Inventory, staff or contractors create sales tax nexus at any revenue at all, which makes the threshold question irrelevant for that state.

Take a seller with 130,000 dollars of sales into Georgia last year, and 60,000 dollars this year.

They still have economic nexus in Georgia, because the previous calendar year already crossed the threshold.

Falling back under the threshold does not undo the obligation. Most states expect you to keep collecting sales tax and to deregister deliberately rather than simply stopping.

Anywhere the answer comes back yes, you have a sales tax permit to apply for. Anywhere it comes back close, you have a date in the calendar to watch.

What your ecommerce platform does not handle

Marketplace laws hand one channel's tax to someone else, which raises a harder question: what happens when you sell through several channels at once?

Work it through. You sell into Florida, a 100,000 dollar state, across three channels:

• Shopify: 45,000 dollars
• Your own Stripe checkout: 40,000 dollars
• Amazon: 30,000 dollars

That is 115,000 dollars in Florida, so you crossed the line some time ago.

But Shopify only sees its own 45,000 and shows you a comfortable margin. Stripe only sees its slice. Amazon only sees its slice. None of them is wrong, and not one of them sees the total that actually matters.

Every channel you add lowers the revenue at which this springs and raises the odds that nobody notices. Reading three dashboards more carefully will not close the gap either. The states measure a combined figure, and each platform is built to report only its own slice.

What platforms genuinely do is calculate tax accurately on their own transactions, and a few will file returns in some states for those transactions. That is useful and it is not the same as compliance. Our post on whether Shopify handles sales tax filing traces exactly where one platform's support stops.

Threshold tracking has to sit above your platforms, on the combined figure, or it is not really happening.

Decision 2: what you owe tax on

Sales tax nexus tells you which states you deal with. Taxability tells you what to charge once you are there, and it is decided product by product, state by state.

Physical goods

The default taxable case, with carve-outs that vary widely. Groceries, prescription drugs and medical devices are commonly exempt.

Clothing shows how uneven this gets:

• Fully exempt in Minnesota, New Jersey and Pennsylvania.
• Exempt below a price cap in Massachusetts and New York.
• Fully taxable in most other states.

Digital products and SaaS

The genuinely difficult category, and the one most guides skip because they are written for physical retailers. An ebook, a downloadable template, a streaming subscription and a piece of hosted software can each land differently inside the same state. Roughly half the states with a sales tax treat specified digital goods as taxable, and a smaller group extends that to SaaS.

The category also moves. Maine began taxing digital audiovisual and digital audio services in January 2026, which pulled streaming and audiobook subscriptions into scope there. If this is what you sell, start with our guides to sales tax on digital products and sales tax for SaaS in the US.

Shipping charges

Three treatments exist across the states: taxable whenever the goods are taxable, exempt when stated separately on the invoice, or taxable either way. We cover the split in is shipping taxable in the US.

Exempt customers

Wholesale buyers, resellers, nonprofits and government agencies can buy tax-free, but only against a valid resale or exemption certificate that you hold and can produce.

This is the part that surprises people in an audit. An untaxed sale with no certificate on file is treated as a taxable sale you failed to collect on. The tax then comes out of your own money rather than the customer's. Certificates are evidence, not paperwork.

Mapping all of this by hand does not scale past a few dozen products, which is what product tax codes are for. Classify a product once and the code carries the correct treatment into every jurisdiction.

Decision 3: how to show sales tax at checkout

You know the rate and whether it applies. Now for the question the other guides leave out entirely: what does the buyer actually see?

Tax-exclusive pricing is the US norm, and the law allows it

American buyers expect a price, then tax added at the end. That convention survived the recent wave of pricing-transparency rules, because those rules were aimed at hidden fees rather than at tax.

The FTC's Rule on Unfair or Deceptive Fees, in force since May 2025, requires a clearly disclosed total price. It permits exactly three exclusions from that price:

• Government charges.
• Shipping.
• Genuinely optional add-ons.

Sales tax is a government charge. California's Honest Pricing Law takes the same line, requiring the advertised price to include every mandatory fee other than shipping and government-imposed taxes.

So adding sales tax at the final step of checkout is lawful. Parking a mandatory "processing fee" next to it is not.

Including tax in the price, and what it costs you

Nothing stops a US seller from advertising 49 dollars and treating that as the total. You back the tax out of what you collected instead of adding it on top.

The catch is arithmetic. Because the sales tax rate is set by the buyer's address, the tax buried inside a fixed price changes with every order.

On that 49 dollar sale, a 6 percent jurisdiction leaves you 46.23 dollars.

A 10.25 percent jurisdiction leaves you 44.44 dollars.

That trade usually favors digital and subscription businesses. A clean round price converts better, and a number that jumps on the last screen does real damage to checkout completion. It usually does not favor thin-margin physical goods. We weigh both sides in the advantages and disadvantages of tax-inclusive pricing.

Either way, show the tax as its own line on the receipt. Several states require the amount to be identified on the invoice even when the displayed price included it.

What changes when you sell into the EU

The first international order is where this stops being a preference and becomes a compliance question, because the European default is the inverse of the American one.

Under Directive 98/6/EC, the selling price shown to a consumer means the final price including VAT and all other taxes. Adding VAT at the last step of checkout, the way you add sales tax in Ohio, is not compliant. The UK, Australia and most GST countries follow the same convention.

A store selling to both markets therefore needs price display to depend on the buyer's location. Tax-exclusive for the US, tax-inclusive for the EU, with the rate resolved before the price renders rather than after. Our guide to handling sales tax, VAT and GST together covers the transition.

Getting the rate right in the first place

All of this assumes the sales tax rate is correct, which depends on sourcing. Most states are destination-sourced, so you use the customer's address. A few are origin-sourced for in-state sales, so you use yours, and some mix the two depending on the transaction.

See origin versus destination sales tax for the distinction.

Accuracy also has to reach below state level. California's Publication 109 sets out the district tax layer, along with the "engaged in business in a district" test that decides whether you collect it.

That sub-state detail is where ZIP-based lookups fail. A single ZIP code can straddle two or more taxing districts, which is why several states publish address-level tools of their own.

Decision 4: how to register, file and remit

The mechanics run in sequence:

1. Register in each state where you have nexus. Apply to that state's department of revenue. Most states register online and issue a sales tax permit either immediately or within about ten business days.
2. Collect sales tax at the correct rate on every taxable sale, and hold the money separately. It is not revenue. Treating collected tax as working capital is how a business arrives at a filing date unable to remit.
3. File sales tax returns on the schedule the state assigns you. Frequency follows your volume, and it changes as you grow.

For step one, have your EIN or SSN, entity type, and business and personal contact details ready. You will also be asked for a NAICS code, and this is where plenty of guides are out of date.

The old catch-all code for online stores, 454110, was retired in the 2022 NAICS revision. Retail is now classified by what you sell, not by how you sell it. An online seller and a physical store selling the same goods share a code.

Look yours up in the NAICS search tool rather than reusing the old one. The full walkthrough is in how to register for a sales tax permit.

There is a shortcut on step one worth knowing about, and worth being careful with. You can register across all 24 Streamlined Sales Tax member states in a single process.

That is efficient. It also registers you in states where you may not yet have economic nexus, and a sales tax registration by itself creates the filing duty. Read what streamlined sales tax is before using it.

Filing frequency is monthly, quarterly or annual depending on your volume, and a state can change yours with little warning. Two more facts catch first-time filers:

• Sales tax returns are reported by jurisdiction. Most states want the breakdown by county, city and special district, not a single statewide figure. If your records only hold totals, every filing means reconstructing the split.
• Zero returns are mandatory. A quarter with no sales in a state where you hold a sales tax permit still needs a return. Skipping it earns a late-filing penalty on zero tax owed, and enough of them can cost you the permit.

Our line-by-line walkthrough of a sales tax return covers due dates, frequency and zero returns in detail. A handful of states also offer a small vendor discount for filing on time, which is worth claiming once you are set up.

What happens when you get it wrong

Sales tax you should have collected does not quietly expire. The state assesses it against you with interest and penalties, whether or not you ever charged the customer.

The dangerous mechanic is the lookback. Statutes of limitation generally start running when a sales tax return is filed, so if you never registered and never filed, the period never starts closing. A business that crossed an economic nexus threshold four years ago and noticed last month is looking at four years of sales tax, not one.

Three situations turn that liability into a real problem:

• An audit. Nexus questionnaires arrive by mail and often precede one. Our sales tax audit guide covers what states ask for and which records hold up. Missing exemption certificates are the most common finding.
• Diligence in a raise or a sale. Unregistered exposure gets quantified during diligence and comes straight off the purchase price, or sits in escrow for years.
• Personal liability. Responsible-person rules in many states let uncollected trust-fund tax follow an owner or officer through the entity.

If you already know you have exposure, the route through it is a voluntary disclosure agreement. Come forward before the state contacts you and most states will cap the lookback, commonly at three or four years, and waive penalties. The Multistate Tax Commission runs a program covering several states through one application.

Once a notice lands in your inbox, that option closes. What happens if you don't collect sales tax sets out the full exposure.

Building an ecommerce sales tax system that scales

None of the four decisions gets harder as you grow. They just get more numerous, which is a different problem. One state and one channel is a spreadsheet. Twelve states and four channels is a system, and the difference is architecture rather than effort.

Job	By hand	With automation
Tracking economic nexus	Export each channel, add the columns, hope you did it recently enough	Every channel rolls into one figure per state, with an alert before you cross
Applying the rate	Sales tax rate tables per state, refreshed manually, ZIP-level at best	Resolved from the customer's address at the moment of sale
Product taxability	A judgement call per product, per state, revisited when laws change	Classified once with a tax code, carried into every jurisdiction
Filing a return	Rebuild the jurisdiction breakdown from raw transactions each period	The breakdown already exists, so filing is a review
Going international	A second tool, a second contract, a second set of rules to learn	VAT and GST run on the same transaction data as US sales tax

That last row is the one worth planning for before you need it. Most US sales tax tools stop at the border, so the day an order arrives from Berlin you start a second procurement process from scratch.

Quaderno was built the other way round. It connects to every channel you sell through and counts them against each state threshold as one figure. It applies the right tax at checkout, whether that means US sales tax added on top or German VAT folded into the price. And it prepares returns in the format each jurisdiction expects, rather than handing you a spreadsheet to reshape.

If you would rather see the field first, we maintain a review of the best sales tax software. There is also a breakdown of what you can hand to a compliance provider, for anyone who would sooner outsource the work than run it.

Wherever you are in this, the next move is the same. Find out which states you have already crossed into, because every other decision follows from that number.