Complete guide: What is nexus and when does your business owe sales tax in another state

You just closed a deal with a customer three states away. Before you celebrate, a question lands hard: do you suddenly owe sales tax there? That’s nexus—and misunderstanding it can cost you. Sales tax nexus determines whether your Florida business must register, collect, and file taxes in another state. Get it wrong, and you face back taxes, penalties, and audit exposure. Get it right, and you move into new markets without that legal fog. This guide walks you through what nexus actually is, when it applies to you, and how to handle it step by step.

Does this apply to your business in Florida?

Yes, if you sell to customers outside Florida—whether that’s goods, services, or both. Sales tax nexus is the legal connection between your business and a state that triggers a tax filing requirement there. The Florida Department of Revenue requires you to register and file where you have nexus, even if you never physically set foot in that state. Every state has different rules, and the rules changed significantly after the U.S. Supreme Court’s 2018 Wayfair decision, which expanded when remote sellers must collect tax.

What nexus really means

Nexus is the term tax authorities use for a sufficient business presence or activity in a state that triggers a filing and collection obligation. Before Wayfair, most states only required sales tax collection from sellers with physical presence—a store, warehouse, or employee. Today, many states use economic nexus instead: if you meet a sales dollar threshold or transaction count in that state, you owe tax there, even if you’ve never been there.

For your Florida business, nexus can arise in four main ways:

• Physical presence nexus: You have an office, warehouse, employee, contractor, or inventory in another state.
• Economic nexus: You exceed that state’s sales threshold (most commonly $100,000 in annual sales into that state).
• Click-through nexus: You pay an in-state affiliate or influencer to refer customers to you.
• Marketplace facilitator nexus: You sell through platforms like Amazon or Etsy that collect tax on your behalf in certain states.

Once you have nexus, you must register for a sales tax permit in that state, collect tax from your customers, and file returns—usually monthly, quarterly, or annually, depending on the state.

The multistate compliance structure

Each state sets its own sales tax rate, rules, and filing deadlines. Florida’s rate is 6% plus a county surtax that varies by county. Other states stack their own rates, exemptions, and special rules on top. When you expand into multiple states, you’re managing multiple tax codes at once.

The structure works like this: you must determine which states you have nexus in, register in each one, calculate the correct rate for each transaction (based on the customer’s delivery address, not yours), collect it at the time of sale, and file the appropriate return by the state’s deadline. Each state’s filing frequency and reporting detail differ. Some require monthly filings; others allow quarterly or annual. Some want line-item transaction detail; others ask only for totals.

The IRS does not manage state sales tax, but your state nexus can intersect with federal income tax responsibilities if you’re selling across state lines. Always confirm current rates, thresholds, and filing deadlines with each state’s revenue department or a tax professional, because these rules change frequently.

How to determine if you have nexus in another state

Start by asking yourself: do I have any of these in State X?

• Physical presence: Office, warehouse, store, employees, or contractor.
• Sales threshold: Have I sold more than that state’s economic nexus threshold (often $100,000) into it this year?
• Affiliate or referral connections: Am I paying anyone in that state to send me customers?
• Marketplace presence: Am I selling through a platform that collects tax on my behalf?

If the answer to any is yes, you likely have nexus. The next step is to register with that state’s revenue department and obtain a sales tax permit. The process is usually online and free; timelines vary from a few days to a few weeks depending on the state’s backlog.

The tricky part: some states’ economic nexus thresholds are transaction-based, not dollar-based. For example, a state might require registration if you make more than 200 sales into it during a calendar year, regardless of total dollars. Track your sales by state carefully. Tools that automatically categorize and report your revenue by destination make this easier—you can then compare the totals against each state’s threshold.

Common mistakes that complicate multistate sales tax

Mistake 1: Thinking physical presence is the only nexus. Many business owners assume they only owe tax where they have an office or warehouse. Under economic nexus rules, a single high-value sale or a series of smaller sales into another state can trigger a filing obligation, even if you’ve never been there. The fix: track your cumulative sales into each state and check each state’s economic nexus threshold annually, not just when you open a physical location.

Mistake 2: Not registering promptly once nexus exists. Once you meet nexus, you have a narrow window—sometimes 30 to 60 days, depending on the state—to register. Delaying registration doesn’t erase your obligation to have collected tax; you’ll owe back taxes plus potential penalties. The fix: set a calendar reminder to review your sales by state at the end of each quarter, and register immediately if a threshold is approached or crossed.

Mistake 3: Using your Florida rate (or your office location’s rate) everywhere. Sales tax rates vary widely by state and county. Using the wrong rate means you either undercollect (and owe the difference later) or overcollect (and must refund the customer). The fix: use tax calculation software or a platform that automatically applies the correct rate based on the customer’s delivery address, not your billing address or the state where you’re based.

Mistake 4: Forgetting about marketplace facilitators. If you sell through Amazon, Etsy, or similar platforms, the platform may collect and file sales tax on your behalf in certain states. That’s good—but it doesn’t exempt you from filing returns in states where the platform doesn’t collect. And if the platform collects in a state, you still need to know this is happening to reconcile your own records and avoid filing duplicate returns. The fix: check your marketplace account settings and contact the platform’s tax support to confirm exactly which states it collects in, then register in the states where it doesn’t.

Filing and ongoing compliance

Once you register, the ongoing process is straightforward but requires attention. You collect tax on each sale based on the customer’s delivery address and the applicable state rate. At the end of your filing period—usually monthly—you total the tax collected and file a return with that state, remitting the tax owed.

Each state has its own portal and deadline. Some allow you to file and pay online; others still use paper forms mailed in. Most states give you 10 to 20 days after the month ends to file. Missing a deadline can trigger penalties, so setting calendar reminders and automating where possible is essential.

The reconciliation step is critical: compare the tax you collected from customers against the tax you remitted to the state. If they don’t match, investigate. Did you apply the wrong rate? Did you exempt a sale incorrectly? Did the state’s rate change mid-month and you missed it? Catching these small errors monthly prevents large problems at audit.

This is particularly important in Florida because the state rule is straightforward: services are not taxable unless listed in the statute, and tangible personal property is taxable unless specifically exempt. As you expand into other states, different rules apply. Some states tax services that Florida doesn’t, and vice versa. Your CPA can help you understand state-specific exemptions, and the role of the revenue department in your home state is walked through step by step in training resources.

What happens if you miss nexus

Misidentifying or ignoring nexus is costly. If you owe sales tax in a state but didn’t register or file, the state can assess you for back taxes, penalties, and interest. Depending on the state and the circumstances, penalties can be substantial. An audit might discover unreported nexus and years of unfiled returns.

The best protection is preventive: track your sales by state, know each state’s economic nexus threshold, and register promptly. If you realize you’ve missed nexus in the past, some states offer voluntary disclosure agreements that allow you to file back returns with reduced or waived penalties. A tax professional can help you navigate this, but voluntary action is far cheaper than being caught by an audit.

For Florida businesses, the Florida sales tax guide covers the details of your home-state obligation, including county surtax variation and exemption rules that often trip up service providers and contractors. Once you understand Florida inside out, expanding out of state becomes a matter of applying the same logic to new rules.

Building a system for multistate compliance

As your business grows into new states, staying organized becomes non-negotiable. Organize your transactions by destination state and sales amount. Review these totals monthly or quarterly against each state’s nexus threshold. Set up a calendar for each state’s filing deadlines. When possible, use tax software or a platform that categorizes transactions automatically and calculates the correct rate by destination—this reduces manual error and saves hours each quarter.

Working with a CPA becomes easier when you bring organized, categorized transaction data to the table. Your advisor can then focus on strategy and risk, not chasing down transaction details. That’s the real value of building a clean system early: it scales with you.

This article is for general educational purposes and isn’t a substitute for advice from a licensed CPA or tax attorney. Rules vary by jurisdiction and change over time—always confirm current requirements with the Florida Department of Revenue or your advisor.

Frequently Asked Questions

What is the difference between physical and economic nexus?

Physical nexus means you have a tangible presence in a state—an office, employee, warehouse, or inventory. Economic nexus means you’ve exceeded that state’s sales threshold (often $100,000 in annual revenue or a transaction count) without any physical presence. Most states now enforce economic nexus, so a single large sale or many small sales into another state can trigger a filing obligation even if you’ve never been there.

Do I have nexus if I sell on Amazon or Etsy?

It depends. Amazon and Etsy collect and remit sales tax on behalf of sellers in certain states, but not all. You have marketplace nexus in those states, but the platform handles collection. However, you must still register and file in states where the marketplace doesn’t collect. Check your seller account settings to see which states the platform covers, then register separately in the others.

How do I know my state’s economic nexus threshold?

Each state publishes its own threshold on its revenue department website. Most use $100,000 in annual sales or 200 transactions as the trigger, but some differ. Search “[State name] economic nexus threshold” or contact the state revenue department directly. Confirm the current year’s threshold annually, because it can change.

What if I already owe sales tax in another state but haven’t filed?

Don’t panic. Some states offer voluntary disclosure agreements that allow you to file past returns with reduced or waived penalties. Consult a tax professional about your situation; voluntary action now is far preferable to being caught in an audit. Acting promptly signals good faith and often results in better terms than if the state discovers the issue on its own.

Does my Florida nexus affect my obligations in other states?

No. Each state sets its own nexus rules independently. Being a Florida resident or having a Florida office doesn’t automatically create nexus anywhere else. You must evaluate nexus separately for each state based on your specific activity there. However, if you have nexus in multiple states, your filing and tax rate obligations compound, so organizing by state is critical.

For the Florida-specific rules behind this, our Florida sales tax guide breaks down rates, deadlines, and filing steps county by county.