For decades, the concept of “nexus”, the connection between a business and a taxing jurisdiction, was relatively straightforward. If you had an office, a warehouse, or an employee in a state, you had a physical presence and, therefore, an obligation to collect and remit sales tax.
However, the digital revolution changed the retail landscape, and the law eventually caught up. Today, physical presence is no longer the sole benchmark, this is where economic nexus and US sales tax obligations come in. For modern businesses, especially those selling online, understanding these rules is no longer optional, it is a critical component of financial risk management.
In simple terms, economic nexus is a tax obligation imposed on out-of-state sellers, including businesses based entirely outside the United States, once they reach a certain level of economic activity within a specific state. Unlike physical nexus, which relies on “bricks and mortar”, economic nexus is triggered entirely by sales revenue or the number of transactions.
The shift toward these rules began in earnest following the landmark 2018 Supreme Court decision, South Dakota v. Wayfair, Inc. Before this ruling, states could only tax businesses with a physical footprint. The Wayfair decision overturned this precedent, acknowledging that in the modern economy, a business can have a substantial impact on a state’s market without ever setting foot in it.
Post-Wayfair, states have the authority to require remote sellers to register, collect, and remit sales tax once they cross specific thresholds. This applies equally to foreign businesses selling into the US as it does to domestic businesses selling across state lines. A company based in the UK, Europe, Canada, or anywhere else in the world is subject to the same economic nexus rules the moment its sales into a given state exceed the relevant threshold. If your business sells goods or services across state lines, you are likely subject to nexus rules in multiple jurisdictions, even if your entire operation is run from a single home office.
Economic nexus isn’t a “one-size-fits-all” rule. Because sales tax is governed at the state level rather than the federal level, each state has the autonomy to set its own triggers. Generally, these triggers fall into two categories:
However, the complexity lies in the nuances. For instance, the “look-back period”, the timeframe a state examines to see if you’ve met the threshold, varies. Some states look at the previous calendar year, while others look at the previous four quarters.
Additionally, what counts as an “included sale” differs. Some states calculate the threshold based on gross sales (including exempt sales and marketplace sales), while others only count taxable sales. If you sell through platforms like Amazon or Shopify, you must also navigate “Marketplace Facilitator” laws, which might count those sales toward your threshold even if the platform collects the tax on your behalf.
Many businesses, particularly those based outside the US, operate under the false impression that economic nexus only applies to American companies selling across state lines. It does not. Any business selling goods or services to customers in a US state, regardless of where that business is incorporated or where it operates from, is subject to that state’s economic nexus rules once the relevant threshold is crossed. This is a dangerous oversight. Sales tax on out-of-state sales can become a liability overnight.
Common business activities that quickly create nexus include:
Relying solely on outdated physical presence tests leaves businesses exposed to unregistered out-of-state obligations. By the time a state sends a nexus questionnaire or an audit notice, the unpaid tax, interest, and penalties can be enough to threaten a company’s solvency. For more on how this impacts international businesses, see our guide on getting a United States EIN vs. a VAT number.
To stay compliant, businesses should treat economic nexus thresholds by state as a dynamic map rather than a fixed list. The landscape is constantly shifting, essentially, states frequently adjust their thresholds or eliminate transaction counts to simplify the burden on small businesses.
When mapping your obligations, look for these patterns:
Because these rules change, it is vital to consult US Sales Tax professionals or use automated tax software to monitor your sales in real-time. For a deeper dive into specific state regulations, explore our state-by-state guides.
Managing sales tax economic nexus by state can feel overwhelming, but a systematic approach can mitigate risk. Follow these practical steps:
1. How did the Wayfair decision change economic nexus rules for remote sellers in the US?
Before the 2018 Wayfair decision, states could only require businesses with a physical presence (like an office or warehouse) to collect sales tax. The Supreme Court ruling changed this, allowing states to tax “remote sellers” based entirely on economic activity. This created the modern “economic nexus” framework, where exceeding a specific dollar amount or transaction count triggers a legal obligation to register and collect sales tax, regardless of physical location.
2. What types of sales count toward economic nexus thresholds in most states?
It varies, but most states look at “gross sales,” which includes taxable goods, tax-exempt sales, and even sales made through marketplaces like Amazon. Some states are more lenient and only count “taxable sales”. It is crucial to check each state’s specific definition, as reaching a threshold with tax-exempt sales may still require you to register and file nil returns to remain compliant.
3. How can a business tell if it must charge sales tax on out-of-state sales?
A business must charge sales tax if it has “nexus” in the buyer’s state. This is determined by checking if you have a physical presence or if your sales volume has surpassed the state’s economic nexus threshold. It is important to regularly run “nexus reports” or have a provider to monitor nexus.
4. What happens if a company surpasses an economic nexus threshold but does not register in that state?
Failure to register creates a “prior period liability.” If a state discovers the nexus (often through audits of your customers or marketplace data), they can demand all uncollected taxes from the date the threshold was crossed. Since the tax wasn’t collected from customers, the business must pay it out of pocket, along with substantial penalties and interest. There is often no statute of limitations for unfiled returns.
5. How often should businesses review their sales data to monitor economic nexus across US states?
At a minimum, businesses should conduct a comprehensive nexus review quarterly. However, for fast-growing companies, monthly monitoring is recommended. Because some states require registration almost immediately after a threshold is met (sometimes by the very next transaction), real-time monitoring through automated tax compliance software is the safest way to avoid falling behind on new obligations.
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