The first thing to figure out is where you actually owe sales tax. Since the 2018 South Dakota v. Wayfair Supreme Court decision, states can require you to collect sales tax even if you have no physical presence there. This is called economic nexus. Most states set the threshold at $100,000 in sales or 200 transactions in a calendar year, but the specifics vary. Some states only use a dollar threshold. A few have lower thresholds. You need to check each state individually.

Track your sales by state throughout the year so you know when you’re approaching a threshold. Once you cross it, you’re required to register for a sales tax permit in that state and begin collecting. Selling without registering after you’ve triggered nexus creates a liability that grows every month you ignore it.

Register for sales tax permits in every state where you have nexus. Don’t collect sales tax in a state where you haven’t registered. That’s actually illegal in some states. The registration process varies but generally involves applying through the state’s department of revenue website. Some states approve you in days, others take weeks.

Configure your e-commerce platform to collect the right amount. Sales tax rates aren’t just state-level. Counties, cities, and special districts can all add their own rates. A customer in Nashville pays a different rate than someone in rural West Tennessee. Shopify, Amazon, and most major platforms integrate with tax calculation tools like TaxJar or Avalara that handle rate lookups automatically. If you’re selling on multiple channels, make sure every one of them is configured correctly.

Filing schedules differ by state and sometimes by your sales volume within that state. Some states want monthly filings, others quarterly or annually. Miss a deadline and penalties start immediately. When you’re filing in 15 or 20 states, keeping track of due dates manually is a recipe for missed filings. This is where sales tax management support or automation software becomes essential rather than optional.

Pay attention to product taxability. Not everything is taxed the same way in every state. Digital goods, clothing, and food items all have different rules depending on the state. What’s taxable in Texas might be exempt in Pennsylvania. If you sell a mix of physical and digital products, you need to understand how each state treats each category.

Marketplace facilitator laws have simplified things for sellers on platforms like Amazon, Etsy, and Walmart. In most states, the marketplace is responsible for collecting and remitting sales tax on your behalf for sales made through their platform. But sales through your own website are still your responsibility. If you sell on both your own site and marketplaces, you need to track which sales the marketplace handles and which ones you handle.

Keep clean records of everything. Every state filing, every payment, every nexus threshold calculation. If a state audits you, they’ll want to see that you tracked your obligations correctly and collected the right amounts. This ties directly into your overall bookkeeping. Clean books make small business tax returns easier and make sales tax compliance far less stressful.

The reality for most e-commerce sellers doing meaningful volume is that multi-state sales tax is too complex to manage with spreadsheets. Between varying thresholds, different filing frequencies, thousands of tax jurisdictions, and changing rules, automation or professional help pays for itself quickly in avoided penalties and saved time.