Sales Tax Is Not Income Tax
Sales tax is collected from the customer and owed to the state regardless of whether the seller has any U.S. income tax exposure at all. A foreign seller with no permanent establishment, no U.S. trade or business, and no federal return due can still be required to register, collect, and remit sales tax in a dozen states. The two systems ask different questions, and a clean answer under one says nothing about the other.
Two systems that do not share a threshold
Federal income tax reaches a foreign person's business profit only if that person is engaged in a trade or business within the United States under IRC §864(b), and then only on income effectively connected with it under §864(c). If a treaty applies and is claimed, the question shifts again to whether the seller has a permanent establishment under the treaty's Article 5. None of that machinery has anything to do with sales tax.
Sales and use tax is a transaction tax, imposed by individual states, collected from the buyer at the point of sale, and remitted by whoever the state's statute designates as responsible for remitting it. It is not a tax on the seller's income or profit. It does not care whether the seller has a U.S. trade or business, whether a treaty applies, or where the seller is resident. A business can be entirely outside the federal income tax net and still have a sales tax collection obligation running in every state where it crosses that state's own threshold, because the two systems measure completely different things.
Physical presence used to be the line, and Wayfair removed it
Before 2018, a state generally could not require an out-of-state seller to collect its sales tax unless the seller had some physical presence in the state, a rule that traced back to National Bellas Hess v. Department of Revenue and was reaffirmed in Quill Corp. v. North Dakota. A seller shipping goods into a state entirely by mail or common carrier, with no property, employees, or agents there, generally fell outside that state's collection authority.
South Dakota v. Wayfair, Inc., 585 U.S. 162, decided by the Supreme Court in 2018, overturned that physical presence requirement as applied to the Commerce Clause. The Court upheld a South Dakota statute that imposed a collection obligation on remote sellers based purely on the volume of their sales into the state, specifically $100,000 of gross sales or 200 separate transactions into South Dakota in the current or prior calendar year, with no physical presence required at all. The decision did not create a single national standard. It removed the constitutional obstacle that had prevented states from taxing on an economic basis, and states then wrote their own economic nexus statutes, most but not all modeled on South Dakota's numbers.
A foreign seller with no U.S. address, no U.S. employees, and no U.S. warehouse can still cross an economic nexus threshold purely by selling enough into a state, and the analysis has nothing to do with residence. A seller does not need to be a U.S. person, or even have any other U.S. contact, to trip a state's economic nexus statute. Selling into the state in sufficient volume is the entire test.
Thresholds are not uniform, and neither is what counts toward them
Most states set their threshold at $100,000 of sales, sometimes paired with a 200-transaction count and sometimes not, but a meaningful number of states use different dollar figures, count only sales of taxable goods toward the threshold, measure the current calendar year only rather than current and prior, or have dropped the transaction-count prong entirely because it swept in high-volume, low-dollar sellers the states did not intend to reach. A seller has to check each state's specific statute rather than assuming South Dakota's numbers apply everywhere, because a threshold that clears in one state can be crossed in the next state over on the same sales figures.
| Element | How it commonly varies by state |
|---|---|
| Dollar threshold | Most commonly $100,000, but some states use $500,000 or other figures |
| Transaction count | Some states pair the dollar figure with a 200-transaction count; many have removed the count prong |
| Measurement period | Some states look at the current calendar year only; others look at the current and immediately preceding year |
| What counts toward the threshold | Some states count gross sales of all kinds; others count only sales of taxable tangible personal property |
| Marketplace sales | Most states exclude sales made through a registered marketplace facilitator from the seller's own threshold calculation, but not all define this the same way |
Marketplace facilitator laws move collection, not always registration
Every state that imposes a sales tax now has a marketplace facilitator statute, which places the collection and remittance obligation on the marketplace itself, rather than on the individual seller, for sales made through that marketplace. A seller who sells exclusively through a registered facilitator such as Amazon, and never through its own storefront, generally does not have to separately collect sales tax on those marketplace sales in states where the facilitator is collecting, because the statute has shifted that specific obligation to the platform.
What the marketplace facilitator statute does not necessarily do is eliminate the seller's own registration or reporting obligation in every state. Some states still require a seller with sufficient marketplace sales volume in the state to register, even though the facilitator handles the collection, particularly where the seller also has any direct sales in that state. A seller who sells both through a marketplace and through its own website has to track the two channels separately, because marketplace sales may already be covered while direct sales through the seller's own storefront are the seller's own unaddressed obligation in that same state, measured against that state's own threshold.
Treaties do not reach this at all
A U.S. income tax treaty's taxes-covered article generally lists specific federal taxes, and typically nothing state-level and nothing beyond income and certain related federal taxes. A no-permanent-establishment position built under a treaty's Article 5 is a position about federal income tax. It has no bearing on a state's authority to require sales tax collection, and no treaty a foreign seller might be resident under changes a state's post-Wayfair economic nexus analysis in any way. This is worth stating plainly because it is the single most common point of confusion in this area: a seller who has correctly concluded there is no U.S. permanent establishment sometimes assumes that conclusion also means no U.S. tax exposure of any kind, and the sales tax analysis proceeds on entirely separate rules that the treaty conclusion does not touch.
Registration and remittance mechanics
Once a threshold is crossed in a given state, the seller generally has to register with that state's revenue department, obtain a sales tax permit, determine the taxability of what it sells under that state's own rules, since taxability of specific product categories varies by state even where the general framework is similar, collect the tax at the correct rate for each sale based on the destination of the shipment in most states, and file returns on a schedule the state assigns based on sales volume, commonly monthly, quarterly, or annually. Rates are not uniform even within a single state, since many states allow local jurisdictions to add their own sales tax on top of the state rate, which means the correct rate can vary by ZIP code within the same state.
A foreign seller registering for the first time generally needs a way to receive mail or communications at a U.S. address for state correspondence, and some states require a responsible party with a Social Security number or individual taxpayer identification number on the registration, which is a practical obstacle worth planning around before the threshold is crossed rather than after a state notice arrives.
What this firm does and does not do here
Ali Gulzari, CPA, EA advises on where a seller's economic nexus exposure exists, how marketplace and direct sales interact with a given state's threshold, and how the sales tax analysis fits alongside the seller's federal income tax position. The firm is not a multistate sales tax returns-filing bureau running ongoing registrations and remittances across dozens of jurisdictions. A seller that has crossed thresholds in a meaningful number of states typically needs a dedicated sales tax compliance platform or provider to handle the recurring registration, calculation, and filing work, and that should be treated as a separate engagement from the advisory work of identifying where the exposure sits in the first place.
What happens when a threshold was crossed and nothing was done about it
A seller who crossed a state's economic nexus threshold in a prior period without registering has generally been out of compliance for that entire period, and the exposure is not limited to the tax itself. Most states impose a failure-to-collect or failure-to-remit penalty on top of the uncollected tax, plus interest running from the original due date of each period's return, and because sales tax was never collected from the customer in the first place, the seller is often the one absorbing the liability rather than passing it through after the fact. Several states also treat an officer or responsible person of the business as personally liable for unremitted sales tax, in a manner similar to the federal trust fund recovery penalty that applies to unpaid employment taxes, which means the exposure does not necessarily stay inside a limited liability entity.
Most states offer a voluntary disclosure program that allows a seller who has not previously been registered to come forward, generally without being identified by name until an agreement is reached, in exchange for a limited lookback period, commonly three or four years rather than the full period of exposure, and a waiver or reduction of penalties. These programs exist precisely because states would rather bring a seller into ongoing compliance than pursue a full historical assessment, and they are generally a materially better outcome than waiting for a state to identify the exposure on its own, whether through a data-sharing arrangement with a marketplace, a referral, or a routine nexus questionnaire.
The Streamlined Sales Tax registration option
The Streamlined Sales and Use Tax Agreement is a multistate effort, joined by a majority of the states that impose a sales tax, to simplify registration and administration for remote sellers specifically. A seller can register through the Streamlined Sales Tax Registration System and obtain registration in every member state through a single application, rather than filing separately with each state's own revenue department. Depending on the seller's sales volume in a given member state, the program also provides access to certified service providers that calculate, collect, and remit the tax on the seller's behalf at no direct cost to the seller in some cases, funded instead by the state, which can materially reduce the administrative burden for a seller newly crossing thresholds in several member states at once. Non-member states still have to be handled individually, so Streamlined registration addresses part of the multistate footprint rather than all of it.
Building the map
Start with a state-by-state sales report covering at least the current year and the prior year, broken out between marketplace sales and direct sales. Compare that report against each state's specific threshold rather than assuming a single national number applies. Confirm which states' marketplace facilitator statutes actually cover the platforms used, and whether any direct sales exist in states where the marketplace is otherwise handling collection. None of this predicts a result for a particular business, and a state's specific threshold, taxability rules, and registration requirements should be confirmed against that state's own current statute before any conclusion is relied on, since these thresholds and rules change by legislative session.