Sales Tax and Nexus: The One SaaS Founders Get Wrong

Sales tax stopped being about where you have an office in 2018. After the Supreme Court's Wayfair decision, states can require you to collect sales tax based purely on how much you sell into them, no physical presence required. That's economic nexus, and it's the trap for startups that sell nationwide from a single California desk.

Nexus is the connection between your business and a state that gives the state the right to make you collect and remit its sales tax. There are two kinds, and startups trip on both.

Physical nexus is the old rule: an office, employees, inventory, or property in a state creates an obligation there. If you store inventory in a warehouse in another state, you likely have physical nexus there.

Economic nexus is the newer, sneakier one. Sell enough into a state, measured by revenue or transaction count, and you can owe there even with no physical presence. Thresholds are set by each state and differ, though $100,000 in sales or 200 transactions in a year is a frequently seen benchmark. California's own threshold differs from that figure, which is part of why you should check each state where you sell rather than assume one number. Cross a state's threshold and you're generally expected to register, collect, and remit there.

Here's where it gets genuinely complicated, and where a blog post can only take you so far. Whether software-as-a-service is taxable depends on the state. Some states tax SaaS as a taxable service or product. Others don't tax it at all. The same subscription can be taxable in one state and exempt in the next.

So the honest answer to "does my SaaS owe California sales tax" is: it depends on what you sell, how it's delivered, and which states your customers are in. This is one of the areas where guessing is genuinely expensive, because getting it wrong in either direction, collecting when you shouldn't or not collecting when you should, creates a mess.

Plenty of startups discover past nexus exposure after the fact, often when an acquirer's diligence team asks about sales tax compliance and finds gaps. The tool for cleaning this up is a Voluntary Disclosure Agreement (VDA): you approach the state proactively, disclose the exposure, and typically get reduced penalties and a limited look-back period in exchange for coming forward.

A VDA is almost always better than waiting for the state to find you. The catch is timing and sequence, which is exactly the kind of thing worth handling with a professional rather than improvising.

→ Know your sales-by-state numbers. You can't assess nexus without them. This is a reason clean bookkeeping matters early.

→ Get a nexus study before you scale. Understanding where you owe is cheaper than fixing years of non-compliance later.

→ Don't assume SaaS is exempt. Taxability varies by state; verify rather than guess.

→ Use a VDA to fix the past. If you've already crossed thresholds without collecting, coming forward voluntarily beats getting caught.

→ Factor it into diligence prep. Sales tax exposure is a standard diligence question. Sort it before you raise or sell, not during.

Sales tax is the tax founders most want to ignore because it feels like an established-company problem. It isn't. A fast-growing SaaS or e-commerce startup can rack up obligations in a dozen states in a single year without noticing. The fix is knowing your footprint before the state, or an acquirer, tells you what it is.