When a U.K. business must register for U.S. sales tax (by state)

• Registration is triggered by activity, not choice. U.K. businesses must register for U.S. sales tax when they exceed state-level nexus thresholds or create physical presence — even without a U.S. entity.
• There’s no single U.S. sales tax system. Each state sets its own rules, thresholds, and filing requirements, making compliance a state-by-state exercise.
• Economic nexus is the most common trigger. Revenue or transaction thresholds can create obligations without physical presence, so sales must be tracked by state, not globally.
• Registration is only the starting point. Once registered, businesses must manage ongoing filing, remittance, and documentation requirements to remain compliant.

Registration for U.S. sales tax means obtaining a permit from a specific state before you collect tax from customers in that state. Registration does not occur automatically, and it’s not optional once a trigger is met.

Each state sets its own rules. There’s no federal (national) sales tax system. This is why U.S. sales tax for European businesses often becomes more complex than expected as operations scale across multiple states.

Registration is the point where legal responsibility begins. Once registered, a business must:

• Collect the correct tax on taxable transactions
• File returns on a defined schedule
• Remit the tax collected
• Maintain records to support compliance

Registration is often confused with filing or reporting. It’s not the same. Registration gives you the authority to collect tax. Filing and remittance are the ongoing obligations that follow.

What sales tax registration enables

Registration allows a business to charge sales tax legally in a state. It also creates a filing cadence. Depending on the state and your sales volume, this may be monthly, quarterly, or annual. These requirements vary and can change over time.

Without registration, a business does not have the legal right to collect tax — even if it believes tax should be applied.

What happens if a business collects tax without registering

Collecting sales tax without being registered creates risk. States can treat this as improper collection. They may require repayment, impose penalties, or assess liability based on transaction history.

More importantly, registration delays often lead to retroactive exposure. If a business should have been registered earlier, states may assess tax, interest, and penalties from the point where the obligation was triggered.

For U.K. businesses, this is where the difference between VAT and U.S. sales tax becomes operational. Registration is not just an administrative step, but the point at which state-level tax compliance begins.

U.S. sales tax registration is triggered by specific activities. These are known as nexus triggers. Once a trigger is met, registration is required in that state.

The shift came from the South Dakota v. Wayfair decision, which confirmed that states can impose tax obligations based on economic activity alone. Since then, most states have introduced economic nexus rules alongside traditional physical presence rules.

In practice, states often combine multiple triggers. A business may meet one or several at the same time.

Economic nexus thresholds

Economic nexus is the most common trigger. Most states apply a threshold of $100,000 in annual sales into the state, or 200 transactions. Some states use revenue only. Others apply both tests.

Once the threshold is exceeded, registration is required — even if the business has no physical presence in that state. This is where many U.K. businesses fall behind. Revenue is often tracked globally, not by state, so thresholds are crossed without being identified.

Physical presence triggers

Physical presence still creates immediate nexus. This includes:

• Employees or contractors working in a state
• Office space or temporary locations
• Attendance at trade shows or events

Even short-term activity can create an obligation. Unlike VAT, where establishment drives registration, U.S. sales tax looks at any operational footprint within a state.

Marketplace facilitator involvement

Marketplace platforms often collect and remit tax on behalf of sellers. However, this does not always remove the seller’s obligations. In some states, sellers must still register, file returns, and maintain transaction records.

States such as California apply stricter interpretations, particularly when businesses also sell directly alongside marketplace channels.

Inventory and third-party logistics triggers

Inventory stored in a state creates nexus immediately. This includes:

• Fulfilment by Amazon (FBA)
• Third-party logistics providers (3PL)
• Warehousing arrangements

Inventory placement is often automated, meaning businesses may have nexus in multiple states without actively choosing those locations. This is one of the most common triggers for U.K. ecommerce businesses.

These operational triggers depend on how your business sells, delivers, and fulfils orders — and they must be monitored continuously as activity grows.

U.S. sales tax registration is determined at state level. The same business activity can trigger an obligation in one state and not in another.

For U.K. businesses, this is where U.S. sales tax jurisdictions become operational rather than theoretical.

State comparison overview

California

California applies a $500,000 economic nexus threshold based on revenue.

Physical presence includes employees, agents, or inventory stored in the state, including fulfilment networks.

Marketplace platforms collect tax in many cases, but sellers must still assess registration requirements where they have direct sales or broader activity.

State guidance from the California Department of Tax and Fee Administration outlines how these obligations are enforced.

Texas

Texas applies a $500,000 revenue threshold with no transaction count.

Physical presence includes inventory, employees, or contractors operating in the state. Marketplace collection does not remove obligations for direct sales.

Detailed rules and filing expectations are set out by the Texas Comptroller for sales tax.

New York

New York applies a combined threshold of $500,000 in sales and 100 transactions.

Inventory, employees, and in-state activity all contribute to nexus. Marketplace rules apply, but sellers must still track thresholds independently.

Requirements and enforcement are defined by New York State Taxation and Finance.

Florida

Florida applies a $100,000 economic nexus threshold.

Physical presence includes events, temporary activity, and inventory. Marketplace platforms collect tax, but direct sales still require compliance.

State rules are administered by the Florida Department of Revenue.

Illinois

Illinois applies a threshold of $100,000 in sales or 200 transactions.

Inventory held in the state and marketplace activity both increase exposure. Registration is expected promptly once thresholds are met.

Guidance is provided by the Illinois Department of Revenue.

Pennsylvania

Pennsylvania applies a $100,000 threshold.

Inventory stored in the state creates immediate nexus. Marketplace facilitators collect tax, but sellers may still have reporting obligations.

State-level rules are outlined by the Pennsylvania Department of Revenue.

Ohio

Ohio applies a $100,000 or 200 transaction threshold.

Physical presence includes inventory, employees, and contractors. Marketplace rules apply, but do not remove all obligations.

Compliance requirements are managed by the Ohio Department of Taxation.

Washington

Washington applies a $100,000 economic nexus threshold and includes broader definitions of taxable activity, covering a wide range of business operations beyond standard retail sales.

Compliance is overseen by the Washington Department of Revenue.

South Dakota

South Dakota applies a $100,000 or 200 transaction threshold and is the origin of the economic nexus model following the Wayfair decision.

Enforcement is active, with clear guidance from the South Dakota Department of Revenue.

Massachusetts

Massachusetts applies a $100,000 economic nexus threshold and enforces compliance through detailed reporting and consistent audit oversight.

Requirements are set out by the Massachusetts Department of Revenue.

Most registration issues come from incorrect assumptions, not lack of effort. U.K. finance teams apply VAT logic to a system that works differently. This leads to missed registrations, incorrect filings, and avoidable exposure.

Registration is not just a formality

Registration is the point where legal responsibility begins. Once registered, a business must:

• File returns on a defined schedule
• Remit any tax collected
• Maintain records to support reporting

Registration does not complete compliance. It starts it. If filings are missed after registration, penalties apply regardless of whether tax was due.

Registration does not equal collection

Registration gives you the authority to collect tax. It does not determine whether tax should be charged. Taxability depends on:

• Product or service type
• Customer status
• State-specific rules

For example, digital services sales tax in the U.S. varies significantly by state, even for the same product. This is why applying a single rule across all states leads to errors.

Zero returns may still be required

In many states, filing is required even when no tax is collected. This creates confusion.

“No sales” is not the same as “no obligation.” Once registered, filing deadlines must be met regardless of activity. Missing zero returns can still trigger penalties.

Voluntary registration does not remove past risk

Some businesses register after discovering they have exceeded thresholds. But late registration does not eliminate exposure. States are likely to assess backdated taxes owed, and impose penalties. Registration should be handled carefully, particularly when historical activity is involved.

For U.K. businesses, registration is not an administrative step. It’s a compliance trigger that brings ongoing obligations — and requires a structured approach from the start.

Managing registration across U.S. states is an ongoing process that needs structure and visibility. For U.K. businesses, the main challenge is shifting from a single VAT system to multiple state-level obligations that change over time.

Build a state-by-state nexus monitoring system

Global revenue tracking is not enough. You need visibility at state level — based on where goods are delivered or services are used. This means capturing accurate location data and monitoring activity continuously.

As your U.S. footprint grows, selling creates obligations that must be tracked at a more granular level. A structured monitoring system should include:

• Revenue by state
• Transaction counts where relevant
• Alerts when thresholds are approaching

Without this, thresholds are often exceeded before they are identified.

Evaluate activity types quarterly

Registration triggers are not limited to revenue. At least once a quarter, review all activity that could create nexus, such as direct sales, marketplace transactions, inventory placement, and use of contractors or affiliates.

This helps identify new exposures early, rather than reacting after the fact.

Maintain registration documentation

Once registered, organisation becomes critical. Keep a clear record of state permits, filing frequencies, and correspondence with tax authorities.

This reduces confusion and supports audit readiness.

Registration doesn’t mean you’re done

Registration is only the first step. Ongoing obligations include:

• Filing returns on time
• Remitting tax collected
• Maintaining exemption certificates
• Responding to state notices or audits

States can still review decisions after registration, including whether nexus was triggered earlier than declared.

Registration must be supported by continuous monitoring, clear processes, and accurate data. Without that, compliance becomes reactive — and risk increases as the business scales.

For many U.K. businesses, U.S. sales tax compliance becomes difficult to manage internally once activity expands across multiple states. This typically happens when:

• Nexus thresholds are approached or exceeded in several states
• Sales channels multiply (direct, marketplace, wholesale)
• Inventory is distributed across fulfilment networks
• Filing obligations increase in frequency and complexity

At this point, the challenge is not just understanding the rules but managing them consistently.

Manual processes break down because they rely on static tracking, fragmented data, and reactive fixes. As the number of states you operate in increases, so does the risk of missed thresholds, incorrect tax treatment, and late filings.

This is where a compliance partner becomes necessary.

Avalara replaces fragmented, manual sales tax processes with a single, automated system designed for multistate compliance.

Instead of tracking thresholds in spreadsheets, Avalara gives you real-time data and AI-driven monitoring to help you identify where nexus is approaching or has already been triggered. This removes guesswork and reduces the risk of late registration.

At the point of transaction, Avalara applies the correct state and local rates based on precise ship-to location and current rules. Product taxability is handled at a granular level, so goods, services, and digital products are treated correctly across different jurisdictions.

Avalara’s AI capabilities help detect anomalies, flag inconsistencies, and continuously improve accuracy across transactions and filings.

The result is a controlled, scalable compliance model. Finance teams spend less time fixing errors and more time supporting growth — with confidence that U.S. sales tax obligations are being managed correctly. Speak with Avalara to find out more.