South Dakota v. Wayfair: The Supreme Court Ruling That Turned Growth Into a Sales-Tax Trap

South Dakota v. Wayfair, Inc. established that a state can force a seller with zero employees, zero offices, and zero warehouses inside its borders to collect and remit that state's sales tax, purely because the seller crossed a revenue or transaction threshold there — and thousands of founders who built their compliance model on the old “no physical presence, no tax” rule have since been billed for years of uncollected tax, interest, and penalties they never saw coming. The June 2018 ruling didn't invent a new tax. It deleted the one legal shield — physical presence — that remote and digital sellers had used for decades to argue they owed nothing to states where they had no footprint at all.

For 26 years, the controlling precedent was Quill Corp. v. North Dakota (1992), which held that under the Commerce Clause a state could not require an out-of-state retailer to collect its sales tax unless the retailer had a physical presence — an office, employees, or a warehouse — inside that state. As e-commerce grew, states argued Quill was costing them billions in uncollected tax on purchases from remote sellers.

South Dakota decided to manufacture a test case. In March 2016 it passed Senate Bill 106, a law requiring any out-of-state seller that delivered more than $100,000 of goods or services into the state, or completed 200 or more separate transactions there, to collect and remit South Dakota sales tax — physical presence or not. Wayfair, Overstock.com, and Newegg all declined to comply, and South Dakota sued them, expecting (and wanting) the case to eventually reach the Supreme Court so Quill could be revisited.

It worked. The Supreme Court heard oral argument on April 17, 2018, and on June 21, 2018 ruled 5–4 in South Dakota's favor. Justice Anthony Kennedy wrote the majority opinion, joined by Thomas, Ginsburg, Alito, and Gorsuch, holding that Quill's physical-presence rule no longer fit an economy built on internet commerce; Chief Justice Roberts dissented, joined by Breyer, Sotomayor, and Kagan, warning that the change was disruptive enough that Congress — not the Court — should have made it. South Dakota's own law took effect for enforcement on November 1, 2018.

States moved fast. By January 1, 2023, every state that levies a sales tax, plus the District of Columbia, had enacted its own economic-nexus statute modeled on South Dakota's, according to reporting in The Tax Adviser (AICPA). The thresholds are not uniform: most states settled on $100,000 in sales, a handful (Alabama, Mississippi) use $250,000, and three of the largest markets — California, Texas, and New York — set the bar at $500,000, with New York additionally requiring more than 100 separate transactions, per 2024 state-by-state nexus data compiled by the Tax Foundation and TaxConnex. South Dakota itself later simplified its own rule: in February 2023 Governor Kristi Noem signed Senate Bill 30 removing the 200-transaction leg entirely, leaving just the $100,000 revenue test, effective July 1, 2023, per Sovos.

The dollar impact for state treasuries has been large. A Government Accountability Office review cited by The Tax Adviser found that reported remote-seller tax collections grew from roughly $3.2 billion across 22 states in 2018 to about $23.3 billion across 33 states by 2021 — more than a sevenfold increase — with marketplace-facilitator collections (Amazon, Etsy, and similar platforms remitting on sellers' behalf) rising from about $344 million in 5 states to roughly $9.8 billion in 21 states over the same period. For software companies specifically, the picture is messier than for physical retailers: whether SaaS is even taxable is its own state-by-state question, and roughly two dozen states — around 25, per guides published by TaxJar and Anrok — tax SaaS in some form, while others tax it only if it involves a download, and several don't tax it at all.

The compliance burden this created for small companies is not theoretical. Engine Advocacy Foundation, a startup-policy nonprofit, documented the case of Geralyn Breig's e-commerce startup AnytownUSA.com, launched with $700,000 in funding: complying with post-Wayfair obligations reportedly meant registering in 44 states, seeing sales-tax software costs jump from about $300 a month to roughly $2,500 a month, and paying around $25,000 to integrate tax calculation into the company's site — on top of legal fees and staff time spent fielding unrelated state paperwork. Multiply that across a country with, by some counts, more than 10,000 distinct state and local sales-tax jurisdictions, and the scope of the problem for a small team becomes clear.

The root cause is a mental model that stopped being true overnight but kept feeling true for years afterward. Before 2018, “nexus” was a physical, binary question: do we have people or property in that state? A founder could answer it once, at incorporation, and forget about it. Wayfair replaced that binary question with roughly 45 separate, continuously moving numbers — one revenue-or-transaction threshold per state, each measured over its own window (current year, prior year, or a rolling twelve months), each capable of being crossed quietly by ordinary revenue growth rather than by any deliberate business decision like opening an office.

The second failure is a tooling gap. Billing and payment systems are built to record revenue, not to flag “you just passed Illinois's $100,000 mark.” Nothing in a typical Stripe or billing dashboard tells a founder they've triggered a new state's tax obligation, so the crossing event is invisible in the moment. It typically resurfaces years later — through an audit, a state's data-sharing agreement with payment processors and marketplace facilitators, or a due-diligence question during a fundraise or acquisition — by which point back taxes, interest, and penalties have been accruing the entire time.

Smart founders miss this precisely because it doesn't look like a legal question anymore — it looks like an accounting footnote. Engineering-minded teams treat tax as a solved, later-stage problem, reasonably assuming that if something needed attention their payment processor would surface it, the way Stripe or similar tools handle EU VAT as Merchant of Record in some flows. Sales tax nexus rarely works that way in the U.S.: the processor moves money, but the legal obligation to register, collect, and remit sits with the seller. And because the thing to watch isn't one number — it's 40-plus independent thresholds, each with its own dollar amount, transaction count, measurement period, and even its own answer to “is our product taxable here at all” — it is far easier to notice a milestone like crossing $1M in ARR than a specific $100,000 mark in a single state nobody was tracking separately.

Any regulatory obligation that used to require a visible, deliberate trigger — opening an office, hiring an employee, shipping a warehouse's worth of inventory — can be redefined by law to instead trigger on an invisible, aggregate metric like revenue or transaction volume. Once that redefinition happens, not knowing you crossed the line is not a defense, and the liability accrues silently until an audit, an investor, or a regulator surfaces it. The general lesson for any company scaling across jurisdictions — states, countries, or otherwise — is to treat “where do we owe money to a government” as a metric you monitor continuously per jurisdiction, not a legal question you answer once at incorporation and never revisit.

The fix is process, not heroics: know your exposure before a regulator finds it for you. A practical compliance loop looks like this.

The case itself was about home-goods and electronics retailers — Wayfair, Overstock.com, and Newegg — but the economic-nexus statutes states subsequently passed apply to whatever each state defines as a taxable sale. That leaves two separate checks for a SaaS company: has it crossed a given state's revenue or transaction threshold, and does that state actually tax software-as-a-service at all? Roughly two dozen states tax SaaS in some form, per guides from TaxJar and Anrok, so the same revenue can be taxable in one state and untaxed in the next.

No — they vary and have changed over time. The South Dakota law that reached the Supreme Court set $100,000 in sales or 200 transactions. Today, per 2024 data compiled by the Tax Foundation and TaxConnex, most states use a $100,000 sales-only test, a couple (Alabama, Mississippi) use $250,000, and three large states — California, Texas, and New York — use $500,000, with New York also requiring more than 100 transactions. South Dakota itself dropped its own 200-transaction test in 2023, per Sovos, leaving only the $100,000 revenue threshold.

States can and do assess back taxes, interest, and penalties once a company is identified — often through data-sharing with payment processors and marketplace facilitators, or through an audit trigger. Many companies address this by pursuing a state's Voluntary Disclosure Agreement (VDA) process, which typically limits the lookback period and can waive penalties, provided it's initiated before the state makes contact; once an audit notice has already arrived, that option is usually off the table and full exposure applies.

This account draws on: the Wikipedia summary of South Dakota v. Wayfair, Inc. for case background, timeline, vote count, and opinion authors; Sovos's explainer on South Dakota's economic-nexus threshold and its 2023 legislative change; the Tax Foundation's glossary entry and 2024 state-by-state economic-nexus data; the AICPA's Tax Adviser retrospective “South Dakota v. Wayfair — five years later,” citing GAO revenue-collection figures; TaxJar's and Anrok's guides to SaaS sales-tax treatment by state; and Engine Advocacy Foundation's reporting on startup compliance costs, including the AnytownUSA.com example.