When Should a Small Business Collect Sales Tax in Multiple States

You sell online from Texas, and orders start rolling in from California, New York, and Florida. Do you owe sales tax in all those states? A decade ago the answer was usually no — but the 2018 Supreme Court decision in South Dakota v. Wayfair changed everything, letting states tax remote sellers with no physical presence. Today, every state with a sales tax sets an “economic nexus” threshold, and crossing it means registering, collecting, and remitting tax there. Here is how to know when you have crossed the line.

What Nexus Means After the Wayfair Decision

Nexus is the connection between your business and a state that creates a tax obligation. Before Wayfair, nexus generally required physical presence — an office, warehouse, or employee. Now, economic nexus based purely on sales volume or transaction count is the standard: most states set thresholds around $100,000 in sales or 200 transactions per year into the state, though the exact numbers vary. Exceed a state’s threshold and you must register for a sales tax permit there, collect the right rate at checkout, and file returns — usually monthly or quarterly. Ignoring it does not make it go away; states share data and audit remote sellers routinely.

Physical Presence Still Creates Nexus Instantly

Economic thresholds get the headlines, but physical presence triggers nexus immediately with no minimum. Storing inventory in an Amazon FBA warehouse in another state, sending employees or contractors to a trade show, having a remote employee working from another state, or using a third-party fulfillment center all create physical nexus. Many sellers discover they have had nexus for years through FBA inventory placement they never tracked. Audit your footprint: list every state where inventory sits, employees work, or you regularly conduct business activity in person.

Marketplace Facilitator Laws Change the Math

If you sell through Amazon, Etsy, eBay, or Walmart Marketplace, those platforms are legally required in most states to collect and remit sales tax on your marketplace sales for you — these are marketplace facilitator laws. That means your Amazon sales may not count toward your own nexus obligations in many states, a huge simplification. But the protection covers only marketplace transactions: sales through your own Shopify or WooCommerce store still count fully. Do not assume you are covered everywhere — map which of your sales channels collect for you and which leave the obligation on you.

How to Track Thresholds Without Losing Your Mind

Manually monitoring 45 different state thresholds is not realistic once you sell nationally. Sales tax software like Avalara, TaxJar, or Shopify Tax tracks your sales by state in real time and alerts you as you approach each threshold. These tools also handle the harder parts: product taxability (clothing is taxed differently across states), correct local rates, exemption certificates, and filing returns. Expect to pay $20-$100+ per month depending on volume — cheap compared to the penalties for non-compliance, which include back taxes, interest, and fines. The SBA’s tax compliance resources explain registration basics for multi-state sellers.

What Registration and Filing Actually Involve

Once you determine nexus in a state, register for a sales tax permit through that state’s department of revenue — most allow online registration in under an hour, and many permits are free. You will be assigned a filing frequency based on volume. Then configure your checkout to collect the correct combined state-plus-local rate for each destination (destination-based sourcing applies in most states). File returns on schedule even for zero-tax periods; skipping “nothing owed” returns triggers notices. Keep exemption certificates for every wholesale or resale customer — auditors ask for these first. State revenue department websites, like the directory of state tax agencies, link directly to each registration portal.

The Voluntary Disclosure Option If You Are Behind

Discovered you should have been collecting for two years? Do not panic and do not ignore it. Most states offer Voluntary Disclosure Agreements (VDAs): you come forward, register, and pay back taxes for a limited lookback period (often 3-4 years instead of unlimited), with penalties frequently waived. A VDA is dramatically cheaper than getting caught in an audit, where the lookback is unlimited and penalties stack. A sales tax consultant can run a VDA across multiple states for a flat fee — money well spent when the alternative is a surprise assessment with interest.

Exemption Certificates: The Paperwork That Saves You

When you sell to resellers, nonprofits, or exempt organizations, you do not collect sales tax — but only if you hold a valid exemption certificate for that buyer in that state. No certificate, no exemption: in an audit, every undocumented exempt sale becomes taxable, plus penalties and interest. Build the habit now: request the certificate before the first exempt sale ships, verify it is the correct form for that state (they differ), check that it is signed and dated, and store it digitally where you can find it in an audit. Set calendar reminders to renew certificates that expire — many states’ resale certificates lapse every few years. Your sales tax software can often manage certificate collection automatically. This is the single most boring and most valuable compliance habit in multi-state selling: auditors ask for exemption certificates first, and missing ones are the easiest assessments to issue.

You owe sales tax in a state when you cross its economic nexus threshold (commonly $100,000 or 200 transactions) or have any physical presence there — inventory, employees, or trade shows. Track thresholds with sales tax software, register before you collect, and use voluntary disclosure if you discover you are already behind.

Conclusion

Multi-state sales tax is complex but manageable: understand economic and physical nexus, let marketplace facilitator laws simplify platform sales, track thresholds with software, register promptly, and file on time. The sellers who get hurt are the ones who assume the rules do not apply to them. A few hundred dollars a year in software beats a five-figure audit assessment every time. For more on running your business right, explore our business guides, meet the team, or ask us anything.

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