Sales Tax Nexus for Online Sellers: When You Owe Tax in Other States

Estimated read time: 10 minutes

Here is a sentence that has ruined many a small seller’s quarter: “I only sell online, so sales tax is not really my problem.” It is your problem. It may not be your problem in every state, but in more states than you think, and the bill tends to arrive as a letter instead of a warning.

The concept at the center of it is called nexus, a fancy word for “enough connection to a state that it can make you collect its sales tax.” Since a 2018 Supreme Court decision, that connection can be created by sales volume alone, no warehouse or office required. If you run an online store, sell on marketplaces, or ship products across state lines, nexus is the single most important sales tax idea to understand.

This guide explains it in plain English: the types of nexus, how thresholds work, what marketplaces handle for you, what they do not, and a practical process for getting compliant without hiring a small army. A necessary note up front: this is educational, not tax or legal advice. Rules differ by state and change often, so confirm specifics with a qualified tax professional or the state’s revenue department.

TL;DR

• Nexus is a sufficient connection to a state that obliges you to register, collect, and remit its sales tax.

• There are two main kinds: physical nexus (inventory, employees, property) and economic nexus (sales or transaction thresholds).

• Many states use a threshold of around $100,000 in annual sales into the state, but thresholds, measurement periods, and transaction counts vary. Check each state.

• Marketplaces like Amazon and Etsy often collect for you, but those sales may still count toward your thresholds, and your own website sales are on you.

• Fix this in order: map where you sell, check where you have nexus, register, automate collection, and file on time.

What nexus actually means

Think of nexus as a state asking, “Are you doing enough business here that we get to treat you like a local?” If the answer is yes, you must register for a sales tax permit, charge the right tax to customers in that state, and send it to the state on a schedule.

The tax itself is paid by the customer. You are the collector. That distinction matters because if you fail to collect it, the state does not usually go after your customers. It comes after you, often for the tax you should have collected plus penalties and interest.

Nexus is determined state by state. You can have nexus in Texas and not in Vermont. You can cross a line in one state this quarter and not have crossed it in any other. That patchwork is exactly why it feels overwhelming, and exactly why a system beats memory.

Physical nexus: the traditional trigger

Physical nexus is the older and more intuitive version. You have it in a state when you have a tangible presence there. Common triggers include:

• An office, store, warehouse, or other property in the state.

• Employees or contractors working in the state, including remote workers.

• Inventory stored in the state, which is the one that surprises online sellers most.

• Attending trade shows or pop-up events and making sales there, in some states.

The inventory trigger catches sellers who use fulfillment programs that spread products across many warehouses. If your goods sit in a fulfillment center in a given state, you may have created physical nexus there even if you never set foot in it. Ask your fulfillment provider which states hold your inventory. If you use a third-party logistics company, our guide to 3PL fulfillment services covers how those networks work.

A remote employee is another common trap. Hiring someone who works from their home state can create nexus there, and not only for payroll tax.

Economic nexus and the Wayfair decision

In 2018, the Supreme Court decided South Dakota v. Wayfair, which allowed states to require out-of-state sellers to collect sales tax based on economic activity alone. After that ruling, nearly every state with a sales tax adopted an economic nexus law.

The typical structure looks like this: if you sell more than a set dollar amount into the state in a defined period, or in some states complete more than a set number of transactions, you have nexus and must register.

A few details that trip people up:

• **Thresholds differ.** Many states use $100,000 in sales, but some larger states use higher figures. Some states have dropped the transaction count test, while others keep it.

• **Measurement periods differ.** Some states use the calendar year, others a trailing twelve months. Some look at the current and prior year.

• **What counts as a sale differs.** States disagree about whether to count exempt sales, marketplace sales, or only taxable retail sales when measuring the threshold.

• **Timing matters.** Many states expect you to start collecting once you cross the threshold, sometimes on the very next transaction or the first day of the following month.

Because these details change, treat any number you read in an article, including this one, as a prompt to check the state’s current rule on its revenue department website.

Marketplaces: what they handle and what they do not

Most states have marketplace facilitator laws. Under these, a platform such as Amazon, Etsy, or eBay is responsible for collecting and remitting sales tax on sales made through its marketplace. That is a genuine relief for sellers who rely on those channels.

But there are limits worth knowing:

• **Your own store is not covered.** Sales through your Shopify, WooCommerce, or Squarespace website are yours to handle. Our guide to ecommerce platforms notes which tools include tax features.

• **Marketplace sales may still count toward your threshold.** In some states they do, which means a seller who earns most revenue on a marketplace can still trigger a registration obligation for direct sales.

• **Physical nexus can still exist.** If you store inventory in a state through a marketplace fulfillment program, that presence may matter for your own sales and other tax obligations.

• **Registration may still be required.** Even when a marketplace collects, some states expect sellers to hold a permit or file returns showing zero tax due.

The safe assumption is that a marketplace simplifies your life without erasing your responsibilities.

Where the sales tax does not apply

A few states have no statewide sales tax: Delaware, Montana, New Hampshire, and Oregon. Alaska has no state sales tax, but some local governments there do charge one, and local rules can add their own wrinkles. If you sell only into those places, the nexus puzzle gets much smaller.

Other things reduce your obligation in specific cases:

• **Exempt products.** Many states exempt or reduce tax on groceries, clothing, or certain digital goods. Rules vary widely and change.

• **Resale and exempt customers.** If you sell wholesale to businesses that provide valid resale certificates, those sales are generally not taxed, but you need to keep the paperwork.

• **Nonprofit and government buyers.** They may be exempt with proper documentation.

If you sell wholesale in volume, our roundup of B2B wholesale ecommerce platforms touches on handling tax-exempt customers.

Origin versus destination sourcing

Once you know you owe tax in a state, you still have to figure out which rate to charge. States generally follow one of two approaches.

In destination-based states, you charge the rate for the buyer’s location. That can include state, county, city, and special district taxes, which means the rate can change from one address to the next. In origin-based states, certain sellers within the state charge the rate based on the seller’s location, though out-of-state sellers often follow destination rules.

This is the part where manual calculation falls apart. Thousands of tax jurisdictions exist, and rates change. Unless you sell only into a handful of places, doing this by hand invites errors. It is the primary reason automation tools exist.

A practical process for getting compliant

If you have never done a nexus review, here is a workable order of operations.

Step 1: Map your sales

Export twelve months or more of sales data by ship-to state, including dollar totals and order counts. Separate marketplace sales from your own channels. A simple spreadsheet is enough.

Step 2: Map your physical footprint

List where you have inventory, employees, contractors, and property. Do not forget fulfillment centers and remote workers.

Step 3: Compare to each state’s rules

For every state where you have meaningful sales or presence, look up the economic nexus threshold and measurement period on the state’s revenue department site. Mark the states where you have crossed or are close to the line.

Step 4: Register before you collect

You generally must register for a permit before you can legally charge tax in a state. Collecting without registering is a problem of its own. Register in each state where you have nexus.

Step 5: Turn on automated collection

Configure your store or tax tool to charge the correct rate in the states where you are registered, and not in the states where you are not.

Step 6: File on schedule

States assign filing frequencies, often monthly, quarterly, or annually based on volume. File even when you collected zero, if the state requires it. Late filing penalties are avoidable.

Step 7: Review quarterly

Check your trailing sales by state every quarter, since thresholds can be crossed quietly during a good sales month.

Tools that take the manual work out

You have three broad options, and the right one depends on volume and complexity.

**Built-in platform tax features.** Many ecommerce platforms calculate tax at checkout based on your settings. They are a good starting point, but they usually do not register you or file your returns.

**Dedicated tax automation services.** Companies such as Avalara, TaxJar, and Stripe Tax calculate rates, track nexus exposure, and in many cases can help with registration and filing, often for additional fees. These tools earn their keep once you sell into many states.

**An accountant or bookkeeper.** For lower volume, a professional who understands multistate sales tax can set up the process and review it periodically. Pair this with a solid accounting platform; our guide to accounting software for small business can help you pick one that integrates with your sales channels.

Whichever route you choose, make sure the tool covers the whole cycle: calculation, registration, filing, and remittance. A calculator that stops at checkout leaves you holding the hardest parts.

What happens if you missed something

If you realize you have been selling into states where you probably should have been collecting, do not panic and do not ignore it. Sales tax liability tends to grow with time, and states generally treat voluntary disclosure far better than discovery by audit.

Many states offer voluntary disclosure agreements that can limit how far back you must pay and reduce penalties. The process usually involves approaching the state, often through a professional and sometimes anonymously at first, to resolve past periods.

The sequence that tends to work: stop the bleeding by registering and collecting going forward, quantify the past exposure with your sales data, and work with a tax professional on the best way to address prior periods. It is far cheaper to deal with this at one year of exposure than at four.

Also keep records. Save your sales data, resale certificates, exemption certificates, and filed returns. If a state ever asks, the person with organized records has an easier conversation.

Sales tax and your broader tax picture

Sales tax is separate from income tax, and it lives in its own world of permits, returns, and deadlines. But it connects to the rest of your finances. Money you collect as sales tax is not revenue. It belongs to the state, and treating it as spendable cash is how businesses end up with a bill they cannot pay.

Open a separate savings account, or at minimum a tracked line in your books, for collected sales tax. Move it out of operating funds routinely. And when you plan your annual tax strategy, our guides to small business tax planning and tax software cover the income side of the picture.

Frequently Asked Questions

Do I need to collect sales tax if I only sell online?

Possibly, yes. Online sellers can have nexus through physical presence or through exceeding a state economic threshold. Whether you must collect depends on the state, your sales volume there, and where you store inventory.

What is the typical economic nexus threshold?

Many states use $100,000 in annual sales into the state, with some also using a transaction count, and a few using higher dollar thresholds. Check each state directly since the rules vary and change.

If Amazon or Etsy collects tax, am I done?

Not necessarily. Marketplaces handle tax on marketplace sales in most states, but your own website sales are your responsibility, and marketplace sales may still count toward your thresholds or require registration.

Do I charge tax before I register?

Generally no. You typically need a sales tax permit in a state before you collect its tax. Register first, then configure collection.

Does drop shipping create nexus?

It can complicate things. Who collects and who holds resale documentation depends on the arrangement and the state, so get professional guidance if you drop ship across many states.

How often do I need to file?

The state assigns a filing frequency, often monthly, quarterly, or annually, based on how much tax you collect. Some states require a return even when no tax is due.

Can I deduct sales tax I collect?

Sales tax you collect is not your income, and you pass it to the state. Tax you pay on business purchases is handled differently, so ask your accountant how to record each.

Related Coverage

• Best Ecommerce Platforms for Small Business: which platforms handle tax settings at checkout
• Small Business Tax Planning 2026: the income tax side of the same calendar
• Best Accounting Software for Small Business: where collected tax should be tracked

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