What is sales tax nexus?

Sales tax nexus is the connection between a business and a state that creates an obligation to collect and remit that state's sales tax. Historically, nexus required physical presence — a store, warehouse, or employee in the state. Since the 2018 South Dakota v. Wayfair Supreme Court ruling, most states have added economic nexus thresholds based purely on sales volume or transaction count, regardless of physical location.

What triggers economic nexus in most states?

The most common threshold is $100,000 in annual sales or 200 separate transactions in a state, matching the original South Dakota standard the Supreme Court upheld in Wayfair. However, thresholds vary: some states use only the dollar threshold with no transaction count floor, others have $50,000 or $500,000 thresholds, and a few use a single statewide transaction as the threshold. Forty-five states plus Washington D.C. have economic nexus laws as of 2026.

Do service businesses have to collect sales tax?

It depends on the state and the type of service. Tangible goods are almost universally taxable when nexus exists. Services are taxable in some states (particularly digital services, software as a service, and certain professional services) but not others. A CPA familiar with multi-state taxation can assess which of your revenue streams trigger tax obligations in which states.

What happens if a business didn't collect sales tax when it should have?

Voluntary disclosure agreements (VDAs) are available in most states — they allow businesses to come forward, pay the back tax owed (often with reduced or waived penalties), and establish clean compliance going forward. VDAs are typically far less expensive than being discovered through an audit. Most tax CPAs recommend pursuing a VDA proactively rather than waiting to be contacted by a state.

Can I use sales tax software instead of a CPA for nexus compliance?

Sales tax automation tools like Avalara and TaxJar handle the calculation and filing mechanics once nexus is established, but they do not advise on whether nexus exists, which products or services are taxable, or how to handle historical non-compliance. A CPA provides the analysis and strategy; the software executes the transactions. Most businesses with multi-state exposure need both.

Sales Tax Nexus for Small Businesses in 2026: What Creates an Obligation and How a CPA Helps

July 22, 2026 · Guide · 7 min read

Sales tax nexus — the legal connection that requires a business to collect and remit a state's sales tax — now exists in 45 states based on sales volume alone, regardless of whether the business has any physical presence there. Since the Supreme Court's 2018 South Dakota v. Wayfair decision, economic nexus rules have proliferated across nearly every state with a sales tax, and small businesses that sell online or serve customers across state lines are often unaware they have obligations they're not meeting. A CPA experienced in multi-state taxation is essential for understanding your current exposure and building a compliant collection process.

The Two Types of Nexus Every Business Owner Must Understand

Physical Nexus (Pre-Wayfair)

Physical nexus is the original standard: if your business has a physical connection to a state — a store, office, warehouse, employee, contractor performing services, or even inventory stored in a third-party fulfillment center (like Amazon FBA) — that state can require you to collect sales tax on transactions with in-state customers. Physical nexus still exists and applies to every state with a sales tax. The Amazon FBA issue catches many sellers off guard: if your inventory sits in a fulfillment center in Texas, you may have physical nexus in Texas regardless of where your business is incorporated or located.

Economic Nexus (Post-Wayfair)

Economic nexus creates a tax collection obligation based purely on the volume of business you do in a state, with no physical presence required. The dominant threshold — mirroring the South Dakota standard upheld in Wayfair — is $100,000 in annual sales to in-state customers or 200 separate transactions in a year. However, the specifics vary significantly by state:

$100,000 / 200 transaction threshold: Most states, including California, Texas, Florida, New York, Illinois, Ohio, and Georgia
Dollar-only threshold (no transaction count): Several states removed the 200-transaction floor; once you hit $100,000 in sales, nexus applies regardless of transaction count
Lower thresholds: A handful of states set the threshold at $50,000 or even lower for specific categories
Higher threshold: A few states (Kansas, notably) initially applied nexus at the first dollar of sales before revising to align with common thresholds

Five states have no sales tax at all: Oregon, Montana, New Hampshire, Delaware, and Alaska (though some Alaska municipalities levy local sales taxes). For businesses in those states, out-of-state obligations can still apply if you're selling to customers in taxing states.

What Products and Services Are Taxable

Nexus only matters if what you're selling is taxable in the relevant state. This is where the analysis becomes genuinely complicated, because taxability rules vary dramatically:

Tangible Personal Property

Physical goods sold to consumers are taxable in virtually every state that has a sales tax, with exceptions for specific categories like groceries (often exempt or partially exempt), prescription medications (almost universally exempt), and agricultural equipment (exempt in many states). If you sell physical products and cross a state's economic nexus threshold, you almost certainly have a collection obligation.

Digital Products and SaaS

Software as a service, digital downloads, streaming subscriptions, and other digital products are taxable in some states and explicitly exempt in others. As of 2026, roughly 30 states tax SaaS to some degree. This has been a fast-moving area of state tax law — if you sell digital products, your taxability analysis must be current and state-specific, not a generalization.

Services

Services are the most variable category. States like New Mexico and Hawaii tax most services. Others (Texas, Florida) tax some services but not others. Most states with sales tax do not tax professional services (legal, accounting, consulting) but do tax specified services like landscaping, software installation, or data processing. The question "are my services taxable?" requires a state-by-state analysis, not a single answer.

How to Assess Your Nexus Exposure

A structured nexus review is the first step for any business that sells in multiple states. Here is what that process looks like:

Identify all states with potential physical nexus: Your state of incorporation, states where employees or contractors work, states where you have inventory (including FBA warehouses), and any states where you have an office, storage, or recurring service presence
Pull 12 months of sales by ship-to state: For each state, calculate total dollar volume and transaction count. Compare against that state's economic nexus threshold
Identify states where you crossed the threshold — and the month it happened, since most states require registration within 30–60 days of crossing the threshold
Assess taxability of your products and services in each nexus state — a state-by-state taxability matrix for your revenue streams
Determine historical exposure: How long have you had nexus without collecting? This determines whether a voluntary disclosure is warranted

For businesses that have been selling across state lines for several years, this analysis frequently reveals past periods of non-collection. A CPA can calculate the estimated tax liability and advise whether pursuing a voluntary disclosure agreement (VDA) is appropriate. Our guide to e-commerce and Amazon seller taxes covers the FBA-specific version of this problem in more depth, including how to identify which states hold your inventory.

Voluntary Disclosure Agreements: Fixing Past Non-Compliance

If a nexus review reveals past periods where you had an obligation but didn't collect, the standard approach is a voluntary disclosure agreement — a formal process where the business comes forward, discloses the prior non-compliance, and negotiates limited back-tax liability with the state. VDA benefits typically include:

Penalty waiver or reduction (usually full waiver of accuracy-related penalties)
Limited lookback period — most states limit the VDA lookback to 3–4 years regardless of how long the non-compliance existed
Interest on tax owed (this is generally not waived — you owe the tax plus interest)
Clean registration going forward with no audit risk for the disclosed period

The alternative — being discovered by a state through audit or data sharing with the IRS or other states — typically results in the full lookback period, full penalties, and interest. For businesses with significant online sales history, the difference between a proactive VDA and an audit-triggered assessment can be tens of thousands of dollars.

Sales Tax Automation Tools and Where CPAs Fit

Sales tax automation platforms — Avalara TrustFile, TaxJar, and Vertex are the three dominant players in 2026 — handle the operational side of sales tax compliance: calculating the right tax rate on each transaction, filing returns in registered states, and tracking registration dates. These tools are useful and increasingly necessary as nexus footprints grow. But they do not:

Tell you whether you have nexus in a given state
Assess whether your products or services are taxable
Advise on historical exposure or voluntary disclosure
Handle audit defense

The CPA provides the strategy and analysis; the software executes the transactions. Most businesses with more than 5–6 nexus states need both. For businesses with fewer nexus states and straightforward product taxability, a CPA for the initial nexus study and setup, followed by software-managed compliance, is the most cost-efficient structure.

Multi-State Tax Filing vs. Sales Tax: A Critical Distinction

Multi-state sales tax compliance and multi-state income tax filing are separate obligations triggered by different rules. Our guide to multi-state tax filing for remote workers and business owners covers income tax nexus — the rules that create an income tax filing obligation in a state. A business can have income tax nexus in a state without sales tax nexus (and vice versa). Both analyses are necessary, and confusing the two is a common source of missed obligations.

What a CPA Should Do for You on Sales Tax

A CPA experienced in multi-state sales tax should be able to:

Conduct a nexus study across all 45 economic nexus states and assess your physical nexus exposure
Produce a state-by-state taxability analysis for your product and service mix
Calculate historical exposure and advise on VDA strategy where applicable
Coordinate registration in new nexus states (including obtaining the right registration type — seller's permit, vendor license, or equivalent)
Recommend and help configure appropriate automation software
Represent the business in the event of a state sales tax audit

Sales tax compliance is one of the areas where the cost of getting it wrong dramatically exceeds the cost of getting professional help early. A nexus study from a qualified CPA typically costs $500–$2,500 depending on complexity — a small investment compared to the penalty exposure of undiscovered non-compliance across multiple states. Find CPAs near you or browse by city to identify firms with experience in multi-state sales tax and e-commerce taxation.

Frequently Asked Questions

What is sales tax nexus?: Sales tax nexus is the connection between a business and a state that creates an obligation to collect and remit that state's sales tax. Historically, nexus required physical presence — a store, warehouse, or employee in the state. Since the 2018 South Dakota v. Wayfair Supreme Court ruling, most states have added economic nexus thresholds based purely on sales volume or transaction count, regardless of physical location.
What triggers economic nexus in most states?: The most common threshold is $100,000 in annual sales or 200 separate transactions in a state, matching the original South Dakota standard the Supreme Court upheld in Wayfair. However, thresholds vary: some states use only the dollar threshold with no transaction count floor, others have $50,000 or $500,000 thresholds, and a few use a single statewide transaction as the threshold. Forty-five states plus Washington D.C. have economic nexus laws as of 2026.
Do service businesses have to collect sales tax?: It depends on the state and the type of service. Tangible goods are almost universally taxable when nexus exists. Services are taxable in some states (particularly digital services, software as a service, and certain professional services) but not others. A CPA familiar with multi-state taxation can assess which of your revenue streams trigger tax obligations in which states.
What happens if a business didn't collect sales tax when it should have?: Voluntary disclosure agreements (VDAs) are available in most states — they allow businesses to come forward, pay the back tax owed (often with reduced or waived penalties), and establish clean compliance going forward. VDAs are typically far less expensive than being discovered through an audit. Most tax CPAs recommend pursuing a VDA proactively rather than waiting to be contacted by a state.
Can I use sales tax software instead of a CPA for nexus compliance?: Sales tax automation tools like Avalara and TaxJar handle the calculation and filing mechanics once nexus is established, but they do not advise on whether nexus exists, which products or services are taxable, or how to handle historical non-compliance. A CPA provides the analysis and strategy; the software executes the transactions. Most businesses with multi-state exposure need both.