Start by confirming where you actually have nexus. Economic nexus thresholds differ by state. Most states trigger a filing requirement once you exceed a certain sales volume or transaction count in that state. The thresholds vary, so you need to check each state individually.

Once you know which states require filings, register with each state’s department of revenue or taxation. Some states have simple online registration that takes 15 minutes. Others require paper applications and can take weeks to process. You’ll receive a sales tax permit and an assigned filing frequency for each state.

Filing frequencies are not uniform. You might file monthly in Massachusetts, quarterly in New York, and annually in a state where you barely meet the threshold. Each state also has its own due date. Most fall around the 20th of the month after the period ends, but there are exceptions. Missing a deadline in one state while you’re focused on another is easy when you’re managing a dozen registrations.

Rates add another layer of complexity. Sales tax is rarely just the state rate. Counties, cities, and special districts often add their own taxes. The rate for a delivery address in one ZIP code can differ from the rate a few blocks away in another jurisdiction. You need to apply the rate based on where the product is delivered, not where your business operates.

Track every deadline in a centralized calendar. Maintain a file with registration confirmations, portal login credentials, and filing confirmations for each state. When a state claims you missed a return from two years ago, you need documentation showing you filed.

Software tools like TaxJar or Avalara can automate rate calculations, generate returns, and sometimes file directly with states. They integrate with your accounting system and pull transaction data automatically. The monthly cost becomes worthwhile once you’re filing in five or more states regularly.

Sales tax compliance across multiple states scales in complexity faster than most business owners expect. Managing three states is annoying but doable. Managing fifteen states with different rules, rates, thresholds, and deadlines becomes a significant time drain.

Many businesses reach a point where the hours spent on multi-state sales tax exceed the cost of having an Andover, MA bookkeeper handle it. If you’re spending more time on compliance than growing your business, that’s usually a sign to get help.