Sales tax nexus is the minimum connection between your business and a state that gives that state legal authority to require you to collect and remit its sales tax. That connection can come from physical presence (people, property, or inventory), from economic activity (enough sales or transactions into the state), or from certain in-state relationships. Five states have no general sales tax at all: Alaska, Delaware, Montana, New Hampshire, and Oregon. Every other state sets its own rules for when an out-of-state seller crosses the line from visitor to tax collector, and since 2018 those rules have expanded to reach sellers who never set foot in the state.
Physical Presence Nexus
The original test was straightforward: if your business had a physical footprint in a state, that state could make you collect tax. The Supreme Court cemented this rule in Quill Corp. v. North Dakota, 504 U.S. 298 (1992), holding that an out-of-state mail-order company with no tangible presence in North Dakota could not be forced to collect the state’s use tax.1Cornell Law Institute. Quill Corp. v. North Dakota (91-0194) Economic nexus has since overtaken it, but physical presence still independently triggers collection duties in every sales-tax state.
The obvious triggers are owning or leasing property: an office, a retail location, a distribution center, even a temporary kiosk at a mall. The definition stretches further than most business owners expect. A single employee working remotely from a home office in another state is generally enough. Traveling sales representatives who visit customers can create the same obligation. Some states set a specific day threshold before in-person activity counts; others treat even a single day of soliciting orders as sufficient.
Inventory is the trigger that catches the most online sellers off guard. If you store goods in a third-party warehouse, you have a physical presence in whatever state that warehouse sits in, regardless of whether you chose the location. Sellers using fulfillment networks like Amazon’s FBA program often discover their inventory has been distributed to warehouses in a half-dozen states they never targeted. Each of those states expects you to register and collect tax on sales delivered to its residents. The inventory doesn’t need to be large or permanent; the mere presence of goods available for sale is enough for most taxing authorities to claim jurisdiction.
Trade shows are another area where rules vary widely. A handful of states set explicit thresholds, such as two or more events within twelve months. Others take the position that attending even a single show where you take orders or make sales creates nexus. If your business exhibits at out-of-state trade shows, checking each host state’s rules before the event is worth the time.
Economic Nexus After Wayfair
The physical presence standard fell in 2018 when the Supreme Court decided South Dakota v. Wayfair, Inc., No. 17-494.2Cornell Law Institute. Wayfair, Inc., et al. Certiorari to the Supreme Court of South Dakota No. 17-494 South Dakota had passed a law requiring out-of-state retailers to collect sales tax if they had $100,000 in sales or 200 transactions delivered into the state in the prior year. The Court upheld that law and overruled Quill, finding that economic activity alone can create a sufficient connection for tax purposes.3Congressional Research Service. State Sales and Use Tax Nexus After South Dakota v. Wayfair Every state with a sales tax has since enacted its own economic nexus law.
The practical consequence is enormous. A business with no employees, no warehouse, and no physical contact with a state can still owe that state collection duties based purely on how much it sells there. For small e-commerce sellers, this turned sales tax compliance from a one-state problem into a forty-five-state problem overnight.
How States Measure the Threshold
Wayfair used South Dakota’s $100,000-or-200-transactions test as its model, but states have not adopted a single uniform standard. The $100,000 revenue threshold is the most common benchmark. Beyond that the details diverge in ways that matter.
Dollar Thresholds and Transaction Counts
Nearly every state with economic nexus uses a $100,000 annual sales threshold, though a few set higher figures. The 200-transaction alternative has been on a steady decline. As of early 2026, roughly 17 jurisdictions still use a transaction-count trigger alongside the dollar threshold. California dropped its transaction test years ago, and Illinois eliminated its 200-transaction threshold effective January 1, 2026. The trend is moving toward dollar-only thresholds, but if your business processes a high volume of low-dollar orders, the transaction count can still trip you up in states that retain it.
Gross Sales Versus Taxable Sales
One of the most misunderstood details is what counts toward the threshold. States generally use one of three measurements: gross sales, retail sales, or taxable sales. Under a gross sales standard, every transaction counts, including wholesale orders, exempt sales, and sales where the buyer provided a resale certificate. Under a retail sales standard, wholesale transactions are excluded, but exempt retail sales still count. Only a taxable-sales standard lets you exclude exempt items from the calculation.4Streamlined Sales Tax. Remote Seller Threshold Terms The distinction matters: a business with $90,000 in taxable sales and $30,000 in exempt sales has crossed a $100,000 gross-sales threshold but not a $100,000 taxable-sales threshold.
Lookback Periods
Most states measure the threshold over the current or prior calendar year. If you exceeded $100,000 in sales to a state last year, you owe collection duties this year even if your current-year sales are lower. A smaller number of states use a rolling twelve-month lookback evaluated quarterly, meaning your obligation can begin mid-year the moment your trailing twelve months of sales cross the line.
When Collection Begins
Crossing the threshold does not mean you owed tax on every sale leading up to it. Most states require you to begin collecting on the next transaction after you hit the threshold, or within a short registration window. You need to be monitoring your sales data in close to real time. Discovering in April that you crossed a threshold the previous November leaves a gap of uncollected tax that becomes your liability.
Affiliate and Click-Through Nexus
Two relationship-based doctrines can create a tax obligation on top of physical presence and raw sales volume.
Affiliate Nexus
Affiliate nexus arises when an out-of-state company has a relationship with an in-state business that helps it reach local customers. The classic scenario involves two companies under common ownership where the in-state entity shares branding, handles returns, or actively promotes the out-of-state company’s products. States treat the local affiliate as an extension of the remote seller, reasoning that the seller is benefiting from a local market presence even without its own employees or offices there. Specifics vary, and some affiliate nexus laws sweep in licensing arrangements and shared distribution agreements.
Click-Through Nexus
Click-through nexus targets a narrower situation: an online retailer pays commissions to in-state residents who refer customers through website links or advertisements. When enough referral sales flow through those links, the state treats the in-state affiliate as providing the retailer with a local market presence. Roughly fifteen states have enacted click-through nexus laws, typically with a minimum referral-sales threshold around $10,000 annually. Its practical significance has faded since Wayfair, because most businesses generating meaningful referral revenue in a state will have already crossed the economic nexus threshold. In a state without economic nexus, or where a seller falls just below the dollar threshold, click-through nexus can still be the trigger.
Marketplace Facilitator Laws
If you sell through a platform like Amazon, eBay, Etsy, or Walmart Marketplace, the tax collection burden has likely shifted off your shoulders for those sales. Every state with a sales tax has enacted marketplace facilitator laws that require the platform operator, not the individual seller, to collect and remit sales tax on transactions it facilitates. The platform handles rate calculation, collection at checkout, and remittance.
The catch: the facilitator’s responsibility only covers sales made through its platform. If you also sell through your own website, at craft fairs, or via any other channel, you are still independently responsible for collecting and remitting tax on those sales. That creates a split compliance environment. You need to track which sales the platform handled and which ones you need to handle yourself.
A second nuance catches some sellers off guard. Even if every single sale you make goes through a marketplace facilitator, some states still require you to hold your own sales tax registration. Whether you need to file returns showing zero direct-sale liability depends on the state.
Registering Once You Have Nexus
Once you determine where you have nexus, the next step is registering for a sales tax permit in each state. Most states offer free online registration, though a few charge small application fees or require refundable security deposits. The real cost is not the permit itself but the ongoing compliance: filing returns on the correct schedule, applying the right tax rates down to the local level, and keeping up with rate changes.
For businesses with obligations in many states, the Streamlined Sales Tax Registration System lets you register in multiple participating states through a single online application.5Streamlined Sales Tax. Registration FAQ As of 2026, twenty-three states are full members of the Streamlined Sales Tax Agreement, with Tennessee as an associate member.6Streamlined Sales Tax Governing Board. State Information Full members include Georgia, Indiana, Michigan, New Jersey, North Carolina, Ohio, and Washington. Businesses that register through Streamlined can also use a Certified Service Provider to handle tax calculation, filing, and remittance. In states where you qualify as a “CSP-compensated seller,” the member states pay the provider’s fees.7Streamlined Sales Tax. What is a CSP
Penalties and Voluntary Disclosure
The consequences for ignoring a nexus obligation are financial and compounding. If a state determines you should have been collecting sales tax and were not, you owe the uncollected tax out of your own pocket, since you cannot go back and charge customers after the fact. On top of the back taxes, states impose penalties that typically range from 5% to 25% of the unpaid amount, plus interest that accrues from the original due date of each unfiled return.
If you discover you have been selling into a state without collecting tax, a voluntary disclosure agreement is usually the smartest path forward. Through a VDA, you come forward to the state, agree to register and begin collecting going forward, and file returns covering a limited lookback period, typically three to four years. In exchange, the state partially or completely waives penalties and agrees not to assess tax for periods before the lookback window.8Multistate Tax Commission. FAQ The Multistate Tax Commission operates a centralized voluntary disclosure program that covers multiple states in a single application.
One category does not qualify for leniency: tax you actually collected from customers but never remitted. States treat that as trust fund money and will pursue the full amount regardless of a VDA. The window for voluntary disclosure also closes once a state contacts you first. If an audit notice arrives before you initiate a VDA, you lose the ability to negotiate a limited lookback and penalty waiver. Businesses that suspect they have unfiled obligations in multiple states are better off acting before the letters start arriving.