State sales tax nexus is the legal connection between your business and a state that gives that state the authority to require you to collect and remit its sales tax. You establish it in one of two main ways: by having a physical footprint in the state, or by selling enough into the state to cross its economic threshold. Affiliate arrangements and marketplace laws create additional triggers. Five states — Alaska, Delaware, Montana, New Hampshire, and Oregon — impose no statewide sales tax, so nexus analysis applies to the other 45 plus the District of Columbia, each with its own rules.
Physical Presence That Creates Nexus
The oldest form of nexus comes from a tangible footprint. A retail store, an office, or a warehouse is the obvious case. The less obvious cases are where most businesses get caught.
A single remote employee working from a home office in another state can create nexus for your business in that state. The employee’s regular performance of job duties there counts as your company doing business in that jurisdiction. Many employers don’t realize a new hire’s home address just created a tax obligation in a state they’ve never visited.
Storing inventory in a third-party fulfillment center also triggers physical presence nexus, even though you don’t own the warehouse. If you sell through Amazon FBA, Amazon may distribute your products across fulfillment centers in multiple states without asking your permission. Inventory sitting on a shelf in a state you’ve never set foot in is enough to establish nexus there. Track where your inventory actually is, because platforms routinely move goods between facilities as demand shifts.
Traveling salespeople and trade show appearances create nexus too. Some states consider even a single day of in-person solicitation enough. If your business has people, property, or products physically located in a state, you almost certainly have nexus there.
Economic Nexus Thresholds
The physical presence standard became far less relevant in 2018 when the Supreme Court decided South Dakota v. Wayfair, Inc., holding that states can require tax collection based purely on the volume of a business’s sales into the state.1Supreme Court of the United States. South Dakota v. Wayfair, Inc. The law at the center of the case set thresholds of $100,000 in annual sales or 200 separate transactions.
Every state with a sales tax has since adopted some form of economic nexus law. $100,000 in revenue remains the most common trigger. The transaction-count threshold, though, is rapidly disappearing. More than a dozen states have already eliminated their transaction-count rules, leaving only the dollar threshold. Any state-by-state analysis still relying on a 200-transaction rule across the board may be outdated.
Gross Sales Versus Taxable Sales
Whether a state counts all sales or only taxable sales toward the threshold matters. States fall into three groups. Those measuring “gross sales” count everything, including exempt transactions and sales for resale. States measuring “retail sales” exclude sales for resale but still count exempt product sales. States measuring “taxable sales” count only transactions that would actually be taxed.2Streamlined Sales Tax Governing Board. Remote Seller Thresholds Terms A business selling mostly exempt products might cross the threshold in a gross-sales state while staying well below it in a taxable-sales state.
Measurement Periods
States also differ in how they measure the timeframe. Some look at the previous calendar year. Others use a rolling 12-month or trailing four-quarter window. A rolling window means you could cross a threshold mid-year and owe registration immediately, rather than waiting for the calendar to turn. Check each state’s specific measurement period to pin down exactly when your obligation began.
Click-Through and Affiliate Nexus
Relationships with in-state third parties can create nexus even when your business has no employees, inventory, or economic activity above the threshold. Click-through nexus applies when you pay a commission to an in-state website owner or influencer who refers customers to you through a link. The in-state referrer is treated as your sales representative. This rule commonly kicks in when referral-generated revenue exceeds $10,000 within a defined period, a threshold used by roughly a dozen states.
Affiliate nexus works similarly but focuses on corporate relationships. If you have a subsidiary, a related company, or a business partner in a state that helps maintain your market by handling repairs, providing customer service, or marketing your products, that related entity’s presence can be attributed to you. States don’t want businesses avoiding collection obligations simply by routing local activity through a separate legal entity.
Marketplace Facilitator Rules
If you sell through a platform like Amazon, eBay, Walmart Marketplace, or Etsy, the platform itself is likely already collecting and remitting sales tax on your behalf. Virtually every state with a sales tax has enacted a marketplace facilitator law requiring the platform, not the individual seller, to handle collection and remittance on facilitated sales.3Streamlined Sales Tax Governing Board. Marketplace Facilitator The platform is treated as the retailer for tax purposes on those transactions.
That doesn’t mean you can ignore nexus entirely. Whether your marketplace sales count toward your own economic nexus threshold depends on the state. Some states exclude marketplace-facilitated sales from your threshold calculation, so only your direct sales (through your own website, for instance) count. Other states include all sales, marketplace and direct, when measuring whether you’ve crossed the line. If you sell through both a marketplace and your own channels, you need to know how each state handles the split. Getting it wrong means either registering when you don’t need to or, worse, failing to register when you do.
What to Do Once You Have Nexus
Register for a Permit
Once you’ve determined where you have nexus, register for a sales tax permit in each state before you continue selling there. Most states offer free online registration, and the majority of permits are issued at no charge. A handful of states charge small fees or require a surety bond for businesses in certain industries, but $0 is the norm for a standard online application.
If you have nexus in several states at once, the Streamlined Sales Tax Registration System lets you register for permits in all 23 SST member states through a single free online application.4Streamlined Sales Tax Governing Board. Sales Tax Registration SSTRS You still file returns and pay each state separately, but the upfront registration is consolidated. Most member states will send registration and reporting information within 15 business days. For non-SST states, you register directly through each state’s tax agency portal. Online applications typically process in a couple of business days; paper applications can take four to six weeks or longer.
Registration forms generally ask for the same core information: your federal employer identification number, the date you first exceeded the nexus threshold or established a physical presence, a description of your business activities in the state, and the type of products or services you sell. Have your sales data organized before you start, because you’ll need to identify the specific trigger date for each state. Keep records of your threshold calculations in case a state later questions when your obligation began.
Collect the Right Rate
Once your permit is approved, you’re legally authorized and required to collect sales tax on transactions in that state. Rates vary not just by state but by county, city, and special taxing district. A single ZIP code can contain multiple tax jurisdictions with different rates. Automated tax calculation software integrates with your e-commerce platform or accounting system and determines the correct rate in real time based on the shipping address, product type, and applicable exemptions. The SST member states provide free rate and boundary databases, and businesses that calculate tax using these official files are held harmless if a rate turns out to be wrong.5Streamlined Sales Tax Governing Board. FAQs – Information About Streamlined
Businesses registered through the SST system can also contract with a Certified Service Provider that handles calculation, filing, and remittance. For sellers without a physical presence in SST member states, the member states compensate the CSP directly, so the service is effectively free for those businesses.6Streamlined Sales Tax Governing Board. Certified Service Providers About Sales processed through certified software generally shield you from audit liability on those transactions.
File on Schedule
After registration, you’ll be assigned a filing frequency: monthly, quarterly, or annually, usually based on sales volume. Higher-volume sellers file more often. Returns are typically due by the 20th of the month following the reporting period, though some states set different dates. Even in months where you have zero sales in a state, you must still file a return showing $0. Failing to file a zero return can trigger penalties just like failing to pay.
Catching Up If You Missed It
If you discover you should have been collecting sales tax in a state but weren’t, a voluntary disclosure agreement is almost always the smartest path. A VDA is a negotiated settlement: you agree to register, file back returns, and pay the tax you owe for a limited look-back period, and the state waives penalties in return.7Multistate Tax Commission. Multistate Voluntary Disclosure Program You still owe the tax itself plus interest, but eliminating penalties makes a significant financial difference.
The Multistate Tax Commission runs a centralized program that lets you negotiate VDAs with multiple states through a single application. MTC staff prepare a draft agreement that goes to each state you’ve selected, and your identity stays confidential until the state signs. Look-back periods generally range from 36 to 60 months depending on the state, and for businesses whose only connection is economic nexus, the look-back typically goes no further back than the state’s economic nexus effective date.8Multistate Tax Commission. Lookback Period Chart
One critical limit: if you already collected sales tax from customers but didn’t remit it, the VDA may not protect you from penalties on those amounts. States treat collected-but-unremitted tax differently because the money was never yours to keep. The look-back period may also extend further back to when you first collected. And if a state has already contacted you about an audit or assessment, VDA eligibility is typically off the table. The program is designed for businesses that come forward before the state comes looking.
Penalties for Getting It Wrong
Penalty rates for late filing or late payment typically range from 5% to 25% of the unpaid tax, and interest accrues on top of that from the original due date. Some states escalate penalties the longer you wait: a return filed 30 days late might trigger a 5% penalty, while one filed 90 days late could reach 10% or more. Fraud-related penalties are dramatically higher.
The part that surprises most business owners is this: sales tax collected from customers is legally a trust fund held on behalf of the state. You never owned that money. If your business collects sales tax and fails to turn it over, whether because of cash flow problems, bookkeeping errors, or deliberate diversion, the state can pursue the individuals responsible, not just the business entity. Officers, directors, and anyone with authority over financial decisions or check-signing power can face personal liability for the full amount of unremitted tax, plus penalties and interest. Claiming ignorance of the tax compliance function is rarely a successful defense if you held a position of financial authority. In serious cases, criminal penalties including fines and incarceration are on the table.
Even if you never collected the tax because you didn’t realize you had nexus, you can still be liable for the amount you should have collected. The state can assess you for the uncollected tax and pursue payment, so the cost comes out of your own revenue rather than having been passed along to customers. That is the practical reason nexus analysis matters: the money you didn’t collect is still money you owe.