What is a Certified Service Provider (CSP)?

A Certified Service Provider (CSP) is a company the states have certified to run your sales tax for you: setting up the software, calculating the tax at checkout, filing the returns, sending the money, and answering the notices. In each member state where you qualify, that state pays the provider and you don’t. Tax on what your own business buys stays with you.

Two questions sit behind that for anyone actually considering one: what is the provider on the hook for, and who is paying them. The certification matters mostly because of the second one. A provider the states have vetted is a provider the states will pay.

What a provider actually does for you

The states fund six specific services when they pay a provider on your behalf. The list belongs to the states rather than to the provider, which is the useful part: it’s the same six whoever you sign with.

• Set up the software and map your catalog to the states’ product categories
• Work out the tax at the point of sale: which state the order belongs to, whether it’s taxable there, and the state and local amount
• File the returns in each member state you’re registered in
• Send the money
• Handle notices and audits from those states, with the supporting paperwork
• Keep your tax data private

Anything past that is an ordinary commercial arrangement. Providers sell plenty beyond the funded six, and they can charge for it.

Who pays for it, and when

In a member state where you qualify, the state pays your provider and the provider can’t bill you for the funded work. The mechanism is worth knowing: the states let a provider “retain a percentage of the sales tax reported and paid on time to that state”. Your provider is paid out of the tax you collect, and only on what lands on time.

Whether a state pays for you is decided state by state, and it turns on how much of your business physically sits there. Four things take you out of the funded category in a member state, and only in that state: an office you keep there more than 30 days, $50,000 or more of property, $50,000 or more of payroll, or 25% or more of your company’s total property or payroll sitting in that one state. A fifth criterion, narrower than it sounds, covers sellers that supply the state itself. The full version, with all five criteria, the lookback period, and what the states count as property and payroll, is the CSP-compensated seller test. Run it before you build a number on any of this.

Everywhere else a provider can charge you: states where you don’t qualify, states outside the program, and work beyond the funded six. There’s also a ceiling on non-taxable volume, set at 30 percent of what a provider processes for you in a member state over a year, past which it can charge you to process those transactions. The paid side is what a certified provider costs.

The arrangement at a glance

Table: the arrangement between a seller, a Certified Service Provider, and the Streamlined member states, at a glance. Checked August 19, 2026.

What it is	A company the member states certified to run your sales tax on your behalf
What it covers	Setup and product mapping, calculation, returns, remittance, notices and audits, data privacy
Who pays	The member state, in the states where you qualify. You, everywhere else
Where it applies	The member states you registered in through the states’ shared system
What stays with you	Tax on your own purchases, your product classifications, other taxes on the same return
What it settles	Nothing about whether your filings are right. That stays each state’s call

Do you have to use one?

No, and most registered sellers don’t. As of July 31, 2026 the Governing Board counted 35,109 active registrations in the shared system, with 29.2 percent of those businesses contracting with a provider. Those figures move every month. Everybody else files their own returns in each state’s own system.

The choice is the one the registration form puts to you: a provider handles your sales tax, or you handle it. If you want the certified tax calculation but intend to keep filing yourself, that’s a Certified Automated System rather than a provider, and the two get mixed up constantly. A CSP and a CAS are different things.

One label to keep straight while you read around this. Contracting with a provider is what makes you a Model 1 seller in the states’ vocabulary. That describes your setup, and it says nothing about who is paying, which is the state by state test above. The terms the program runs on holds the rest of the vocabulary, including the Agreement’s own one sentence definition of a CSP, word for word.

What a provider doesn’t take off your plate

Appointing one hands over the collecting, the filing and the paying. It doesn’t hand over everything, and this is the part people find out about afterwards.

• Your own purchases stay yours. A provider handles tax on what you sell, not the use tax you owe on what your business buys. Ask whether they will report it for you. If they don’t, that return goes to the state directly from you.
• Your product classifications stay yours. Mapping your catalog to tax categories is the step with judgment in it, and it’s the step the relief doesn’t reach: “You will not receive liability relief if you or the CSP incorrectly classify your product into an incorrect product category or to an incorrect tax rule.” A provider that does your mapping owns its mistakes there. Where you did the mapping, it can bill you to put it right.
• Other taxes on the same return stay with you. If your state sales tax return also carries something like lodging or tourism tax, that part is still yours to file.
• Coverage stops at the member states where you qualify. There are 24 member states: 23 full members plus Tennessee, the only associate member, and whether the states’ funding of providers reaches an associate member has no published answer, which is why 23 is the number to plan against. Outside those states, everything a provider does for you is ordinary paid work.
• Certification is not a verdict on your filings. It gets you liability relief where a state’s own rate or taxability data was wrong. Each tax authority still decides for itself whether what you filed was right.

Where to go next

If you’re still deciding whether any of this is worth it, start with what the SST program actually is. If you’ve decided, registering is one application, and a provider will usually do that part for you. If the question is money, the paid side is what a certified provider costs.

Nothing here is tax advice, and whether you’re required to collect anywhere is a question for your accountant and for the state.