SaaS sales tax: which US states actually tax software

Two things have to be true before you owe sales tax on a subscription. You must have nexus in the state, and the state must treat what you sell as taxable. Founders usually check neither and then discover both at once, typically during diligence.

The good news is that the analysis is finite. There are forty-five states plus the District of Columbia with a sales tax, five with none, and the taxability answer for software falls into four recognisable groups.

Nexus: when a state can reach you at all

Since the Supreme Court's 2018 decision in *South Dakota v. Wayfair*, a state may require an out-of-state seller to collect its sales tax based on economic activity alone — no office, no staff, no server required.

• Economic nexus is the common trigger: typically $100,000 of sales into the state in the current or prior year. Some states use a higher figure, and a shrinking number add or use a 200-transaction count. Several have repealed the transaction test precisely because it caught small sellers with cheap products.
• Physical nexus still exists and still comes first: an employee, a contractor in some states, inventory in a warehouse, or attending a trade show can create it with no revenue threshold at all.
• Marketplace facilitator laws shift collection to the marketplace. If you sell through an app store or a marketplace, that platform is generally collecting and remitting on those sales, and they may not count toward your own threshold.

Taxability: the four groups

Two observations founders find counter-intuitive. California does not tax SaaS — the largest market in the country is frequently the one you do not collect in. Delaware taxes nothing, which has no bearing on your obligations elsewhere and is not a reason to incorporate there.

The definitions that decide it

Whether your product is taxable often turns on how you describe it, and the categories are older than the products:

• Prewritten (canned) software — taxable in most states, including when delivered electronically. If you sell a licence to download, you are probably here.
• Custom software — usually exempt, but the definition is narrow. Configuring a standard product for a customer is rarely custom software.
• Software as a service — the contested category, and the one the table above maps.
• Digital products — e-books, media, courses. A separate category with its own state-by-state answer, often different from SaaS in the same state.
• Professional services — implementation, consulting and support. Frequently exempt, and frequently taxable if bundled with a taxable item on one line. Separately state them on the invoice.

Exemptions you should be collecting

Not every customer in a taxable state is a taxable sale. Resellers, some non-profits and government purchasers can be exempt — but the exemption belongs to the buyer and you have to hold the exemption or resale certificate to support not charging.

Collect them at signup, store them against the account, and diarise expiry where the state imposes one. In an audit, an uncollected certificate means you owe the tax you did not charge, which is the same failure mode as the VAT case: the customer is gone and the liability is not.

What it costs to comply, and the alternative

Registering in a state means a permit, periodic returns whether or not you had sales, and a rate calculation that has to handle local jurisdictions — several states have hundreds of them. Ten states means ten filing cadences.

So the practical choice is the same as it is in Europe:

1. 1A merchant of record sells as principal and takes on the obligation entirely. Highest fee, lowest attention, and the right answer for most self-serve products below meaningful scale — what a merchant of record actually is.
2. 2A tax engine on your own processor calculates and files but leaves the registrations and the liability with you. Cheaper, and requires you to actually run the registrations.
3. 3Doing nothing deliberately while below every threshold, monitored monthly. Legitimate, and only legitimate while it is actually true.

If you have already missed it

Uncollected sales tax does not expire quietly. In most states the statute of limitations does not begin to run until a return is filed, so an unregistered seller has open exposure back to the day nexus began, plus interest and penalties.

The remedy is a voluntary disclosure agreement. Approach the state before it approaches you, typically through an adviser and often anonymously at first, and states will commonly limit the look-back to a defined period and waive penalties. The relief is not available once they have contacted you — which is the entire reason to deal with this before an acquirer's diligence team finds it and holds back part of the price.