United States / Guides / Sales tax nexus: why nobody can answer it in a blog post
United States · guideSales tax nexus: why nobody can answer it in a blog post
The short answer
Sales tax nexus is the connection between a business and a state that obligates the business to register, collect, and remit that state's sales tax. Before 2018, nexus generally required physical presence — an office, employees, or inventory in the state. The Supreme Court's decision in South Dakota v. Wayfair, Inc. (June 21, 2018) added a second path: economic nexus, where crossing a state-set dollar or transaction threshold on sales into that state creates the same obligation with no physical presence at all. Every state that taxes sales sets its own threshold, its own effective date, and its own rules for what counts toward it, so there is no single number that applies everywhere, and whether a specific business has crossed a specific state's line is a determination made against that business's own sales data and that state's current statute — not something a generic guide can answer for it.
Key facts — verified dates on each
What nexus meant before Wayfair, and what changed
For decades, the controlling rule was physical presence: a state could require a business to collect its sales tax only if the business had some physical footprint there — a retail location, an office, employees working in the state, or inventory stored in a warehouse the business controlled. A business with no people, property, or inventory in a state generally had no sales tax collection obligation to that state, no matter how many customers in that state bought from it by mail order or, later, online.
That rule came from two older Supreme Court cases, National Bellas Hess (1967) and Quill Corp. v. North Dakota (1992), and it held for national e-commerce's entire early growth period. States argued it cost them enormous uncollected use tax as online sales grew, and in 2016 South Dakota passed a law designed to force the issue: it asserted sales tax collection authority over any remote seller crossing a dollar or transaction threshold, with no physical presence required, daring retailers to challenge it in court.
Wayfair, Overstock, and Newegg did challenge it, and the case reached the Supreme Court. On June 21, 2018, the Court ruled 5-4 in South Dakota's favor, overturning the physical presence rule as "unsound and incorrect" for a modern economy where a seller can have substantial economic contact with a state's market without ever having a person or a building there.
Economic nexus: a second path to the same obligation
Wayfair did not eliminate physical-presence nexus — a business with an office or employees in a state still has nexus there the old way. What it added is a second, independent path: economic nexus, triggered when a remote seller's sales into a state cross that state's own statutory threshold, typically measured in dollars, sometimes also in transaction count, over a look-back period the state defines (commonly the current or prior calendar year).
Every state that levies a general sales tax has since enacted its own economic nexus statute modeled on South Dakota's, but "modeled on" does not mean identical. States set their own dollar figures, decide independently whether to also test transaction count, define differently what counts toward the threshold (gross sales, taxable sales, marketplace-facilitated sales, exempt resale transactions), and set their own effective dates — some in 2018 or 2019, some later, some revised again since.
South Dakota's own rule illustrates that states keep moving these targets after the fact. The original 2016 law set the threshold at $100,000 in gross sales or 200 separate transactions into the state. Effective July 1, 2023, South Dakota removed the 200-transaction leg entirely, leaving a single $100,000 gross-sales test — the same state that started the whole framework changed its own rule five years after Wayfair was decided.
Why one number never answers the question for every state
California's threshold illustrates the same point from a different state: since April 1, 2019, an out-of-state retailer with more than $500,000 in total combined sales of tangible personal property delivered into California during the current or preceding calendar year must register with the California Department of Tax and Fee Administration and collect California sales and use tax — a sales-only test, with no transaction-count leg at all, at five times South Dakota's dollar figure.
Two states, two different numbers, two different test designs, both descended from the same Supreme Court decision. Multiply that by every other state that taxes sales, each running its own legislature on its own schedule, and the reason a single blog post cannot hand a business a definitive nexus map becomes structural rather than a gap in research: the underlying data is not one fact, it is dozens of independently maintained facts that can each change in an ordinary legislative session.
Marketplace facilitator laws add a further layer that changes who has the collection duty even when the underlying sale is the same. Most states now require platforms like Amazon, Etsy, or Shopify's own marketplace features to collect and remit sales tax on behalf of third-party sellers using them, which can mean a seller's marketplace sales are already covered even while their direct website sales into the same state are not — two channels, two different answers, inside one business.
Physical presence nexus has not gone away either
A business can still trigger nexus the pre-Wayfair way, and this path is easy to miss because it does not show up in a sales-by-state report at all. Remote employees working from a state, inventory held in a third-party fulfillment or warehousing arrangement in a state (including inventory placed by a marketplace's own fulfillment network without the seller choosing the location), attending a trade show, or maintaining even a small local presence can each independently create physical nexus regardless of sales volume.
Some states also apply click-through or affiliate nexus rules, attributing nexus to a business through in-state affiliates or referral partners who earn commission on sales, and a small number apply "trailing nexus," where an obligation to collect can continue for a period after the activity that created it stops. None of these turn on a single dollar figure a company can check against its own revenue report — they turn on facts about people, property, and relationships that live outside the accounting system.
What bookkeeping can put on the table — and what it cannot decide
A nexus determination starts with data the business's own books should already hold: sales by state, broken out by channel (direct website, each marketplace, wholesale), by month, against a running current-year and prior-year total. Without that breakdown, the first question in any nexus review — "how close are we to each state's threshold, and when did we cross it if we did" — cannot be answered at all, because the underlying transactions were never organized by destination state in the first place.
This is where clean, channel-level bookkeeping earns its keep: reconciled sales data that ties to actual ship-to states, separated by marketplace-facilitated versus direct sales (since the collection duty can sit with the platform for one and the seller for the other), and available as a running total rather than reconstructed after the fact when a state notice arrives. CapEasy's bookkeeping and financial reporting support builds and maintains that record.
What that record does not do is decide the legal question. Whether a specific business has crossed a specific state's current threshold, whether a physical-presence or affiliate-nexus rule applies to its particular facts, and what registration and collection obligations follow from either are determinations made by the business's CPA or a state and local tax (SALT) attorney, working from the sales data and the state's current statute — not a conclusion bookkeeping software or a bookkeeper reaches on the business's behalf.
The figures, and when we checked them
These numbers change by year or by notification. Each one shows the date we last verified it against the source — if that date looks old, check the source before relying on it.
Questions on this
What is sales tax nexus?
Nexus is the connection between a business and a state that gives the state authority to require the business to register, collect, and remit that state's sales tax. It can arise from physical presence in the state or, since 2018, from economic activity in the state alone.
What did South Dakota v. Wayfair actually change?
Before the June 21, 2018 decision, a state generally could not require a business to collect its sales tax unless the business had a physical presence there. Wayfair overturned that limit, allowing states to impose an economic nexus test based on sales volume into the state, with no physical presence required.
Is there one nationwide economic nexus threshold?
No. Each state that taxes sales sets its own threshold, and the figures are not uniform — South Dakota currently uses $100,000 in gross sales with no transaction-count test, while California uses $500,000 with no transaction-count test. Other states set different dollar figures, some still include a transaction-count leg, and the rules can change in any legislative session.
Does economic nexus replace physical presence nexus?
No, it is added on top of it. A business with employees, an office, or inventory in a state still has nexus there through the physical-presence path, independent of its sales volume into that state.
If I sell only through Amazon or another marketplace, do I still need to track nexus?
Most states now require the marketplace to collect and remit sales tax on the seller's behalf on marketplace-facilitated sales, but that duty typically does not extend to a seller's direct website or wholesale sales into the same state. A business selling through more than one channel can have its marketplace sales covered while its direct sales are not, which is a fact worth confirming channel by channel rather than assuming.
Can inventory stored in a fulfillment network create nexus even if I never chose that state?
It can, in states that treat inventory physically present in the state — including inventory a fulfillment network placed there without the seller's direct choice — as physical-presence nexus. This is a fact pattern worth raising with a CPA or SALT attorney specifically, since it will not appear in a sales-by-state revenue report.
How often do state thresholds change?
Often enough that a figure verified two years ago should not be assumed current. South Dakota itself amended its own original threshold in 2023, five years after starting the framework in Wayfair. Any number should be checked against the specific state's current statute or department of revenue guidance before being relied on.
What data do I need before a nexus review can even start?
Sales broken out by ship-to state, by channel (direct versus each marketplace), by month, with running current-year and prior-year totals. Without that breakdown organized by destination state, a CPA or SALT attorney has nothing to test against each state's threshold.
Does CapEasy determine whether my business has nexus in a state?
No. CapEasy's bookkeeping and financial reporting support organizes sales data by state and channel so the question can actually be tested. Determining whether that data crosses a specific state's current threshold, and what to do about it, is a legal and tax determination made by the business's CPA or a state and local tax attorney.
What happens if a business has nexus in a state and does not register?
Consequences vary by state and are set by that state's law, typically including back tax, penalties, and interest reaching back further than a business might expect. The specific exposure for a given business and state is part of what a CPA or SALT attorney evaluates as part of a nexus determination, not a figure this guide can state in general terms.
Primary sources
- South Dakota v. Wayfair, Inc., 585 U.S. ___ (2018) — opinion of the Court (Supreme Court of the United States)
- South Dakota Department of Revenue — Sales & Use Tax / Remote Sellers
- California Department of Tax and Fee Administration — Registration Requirements for Out-of-State Retailers
Last reviewed 2026-08-14. Statutes and schedules change — the sources above are authoritative, this page is orientation.
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