US sales tax registration and filing after nexus
Establishing that a business has US sales tax nexus is only the start. Nexus is the legal trigger; what follows is a set of practical obligations in every state where that trigger has been pulled — registration, collection and filing. Because sales tax in the United States is a state matter with no federal layer, a business that sells across the country can find itself managing many separate state relationships at once. This guide sets out what to do once nexus exists.
From nexus to obligation
Nexus is the connection between a business and a state sufficient for the state to require sales tax collection. It arises through physical presence — an office, employees, inventory in a warehouse — or, since economic nexus rules spread, through exceeding a sales or transaction threshold into the state. The detail of how nexus is established is covered in US sales tax nexus for e-commerce. Once nexus exists in a state, three obligations follow in that state, and they are the subject of the rest of this guide: register, collect, file.
Registering for a permit
The first step in each nexus state is to register for a sales tax permit (also called a seller's permit or sales tax license) with that state's tax authority, before collecting any tax. The order matters: collecting sales tax without a permit is itself a problem in many states, because the business is holding tax it has no authorisation to collect. Registration typically requires the business's details, its federal EIN, and information about its activities in the state. There is no federal registration to fall back on — the United States has no national sales tax — so each state stands alone, and a multi-state seller registers state by state.
We prepare the schedules and bookkeeping, and a licensed US professional signs where the law requires it.
Avail our US tax desk servicesCollecting at the right rate
Once registered, the business collects sales tax on its taxable sales into the state. The rate is rarely a single number, because US sales tax stacks:
- A state rate, plus
- local rates — county, city and special-district taxes — that vary within the state.
The combined rate generally depends on the buyer's location for most sales, which means a business shipping to different addresses within one state may apply many different combined rates. Two further complications matter: not all products are taxable (many states exempt categories such as certain groceries or clothing), and some customers are exempt (resellers with a valid certificate, for instance). Getting the rate and taxability right per sale is the operational heart of sales tax compliance, and it is where automation earns its cost for any seller of scale.
Filing and remitting
Collection is not the end — the tax collected has to be reported and paid over. On registering, the state assigns a filing frequency — monthly, quarterly or annually — usually based on expected volume. Each period the business files a sales tax return reporting taxable sales and tax collected, broken down as the state requires (often by jurisdiction), and remits the tax. Two disciplines prevent most problems:
- File every period, including zero returns. A registered seller generally must file even when no tax was collected; a missed filing is a compliance failure regardless of the amount.
- Remit on time. Late remittance draws penalties and interest, and the money was never the business's to keep — it was collected on the state's behalf.
Managing multiple states
The real challenge is not any single state but the aggregate. A business with nexus in many states runs many registrations, rate calculations and filing calendars at once, each with its own rules and deadlines. This administrative load is why sales tax nexus is such a significant consequence of growth, and it connects to the wider picture of federal versus state tax filing and the separate state charges examined in franchise tax versus income tax. A seller structured as an LLC should also keep the sales tax obligations distinct from its income tax classification under single- versus multi-member LLC treatment — they are separate systems that happen to apply to the same business.
Sources
This guide is written against the official and clearly labelled professional references below. Rates, thresholds and portal procedures change between reviews, so open the primary source before relying on a figure.
Questions people also ask
Once I have nexus, what do I actually have to do?
Three things, per state: register for a sales tax permit before you start collecting, collect sales tax at the correct combined rate on your taxable sales into that state, and file sales tax returns on the schedule the state gives you, remitting what you collected. Nexus is the trigger; registration, collection and filing are the obligations that follow it in each state where it exists.
Do I register for sales tax with the federal government?
No. The United States has no federal sales tax. Sales tax is administered by individual states (and many local jurisdictions within them), so you register with each state's tax authority separately. This is why a business selling nationwide can end up with dozens of state registrations — there is no single national registration that covers them all.
Do I have to file a sales tax return even if I collected nothing?
Usually yes. Once you are registered in a state, that state generally expects a return every filing period even if you made no taxable sales — a "zero return." Skipping a filing because there was nothing to remit is a common way registered sellers fall out of compliance and trigger penalties, so the safer rule is to file every period the state assigns until you formally close the registration.
Send the tax year and the transaction or filing involved, and we will tell you what is actually required.
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