SaaS Nexus and Sales Tax: A Checklist From Thresholds to Registration

Nexus comes from two families of triggers. Physical nexus arises from employees, contractors, offices, inventory or equipment in a state, and remote workers count. Economic nexus arises when your sales into a state pass a dollar amount, a transaction count or both, measured over a period the state defines.

Start by mapping your customers to states using the customer's billing and usage location, not your own address. Then compare each state's sales over its measurement period to its published threshold. Some states measure calendar years, others use a rolling twelve months, and some count only taxable sales while others count all sales.

Growth makes this a moving target: your sales into a state rise with your revenue, so a state that was under its threshold last year can cross it this year. Recheck at least quarterly, and set an internal alert well below each threshold.

Taxability differs, and nexus without taxability means no tax to collect. States treat SaaS in several ways: as taxable prewritten or canned software, as a taxable digital product, as a service that is only sometimes taxable, or as not taxable at all. Rules can also differ for business customers and consumers, and for exemptions such as resale or manufacturing.

For each state where you have nexus, record the answer, the authority for it and the date you checked. Use the state revenue department's guidance and ask a tax professional to confirm gray areas, because a wrong assumption can create a liability that compounds for years.

Keep customer exemption certificates for tax-exempt buyers. Without a valid certificate on file, a state can hold you responsible for tax you did not collect.

Run this sequence, and repeat the first three steps each quarter:

1. Export sales by customer state for the period each state measures.
2. Compare totals and transaction counts to each state's threshold.
3. Confirm taxability of your product in every state that is close or over.
4. Register in each state where you have nexus and your product is taxable, and do so promptly after crossing the threshold.
5. Set up tax calculation in your billing system by customer location and product type.
6. Collect exemption certificates and store them by customer.
7. File and remit on the schedule the state assigns you, even if the return shows zero.
8. Reconcile the tax collected to your sales tax liability account each month.

The 45-state economic nexus guide covers the state-by-state detail. Tools that automate calculation and filing are compared in a guide to sales tax tools for SaaS, and billing platform options in a billing platform comparison.

Exposure generally starts when you crossed the threshold, not when you noticed. If you sold taxable subscriptions and did not collect, the state may hold you liable for the tax, plus interest and possibly penalties, even if your customers would have paid it.

Voluntary disclosure agreements, or VDAs, are the usual remedy. Many states offer them, typically limiting how far back you must pay and often reducing penalties, but they generally require that you come forward before the state contacts you. Ask a tax professional to run the numbers and approach states in order of exposure.

Say you crossed a state's threshold four years ago and never registered, and that state's VDA program limits the lookback to three years. You would pay three years of tax instead of four, so coming forward before an inquiry can remove a full year of exposure. Whether penalties and interest are also reduced varies by state, so confirm the terms with a tax professional before you contact any state.

Compliance works best when tax logic sits in the billing flow instead of a spreadsheet. Your billing system should capture the customer's location, apply the correct tax and show it on the invoice. Finance then reconciles the tax collected to the filings.

Three habits prevent most problems:

• Store the tax address and the exemption status on the customer record and review changes.
• Reconcile the sales tax liability account before each filing.
• Keep a state-by-state log of registrations, filing frequency, IDs and due dates.

Customer changes need a process too. If a customer moves its billing address mid-contract, update the tax address from the effective date and check whether the new state changes taxability or your nexus totals. If one customer uses the product from several states, document how you decide which location governs and apply it the same way each time. Sourcing rules vary by state, so confirm your approach with a tax professional.