Expanding your UK business into the United States is one of the most exciting growth leaps you can take. With a consumer market that dwarfs the UK, the potential for scale is massive. However, as we move into 2026, the US tax landscape has become significantly more complex for international sellers. The Internal Revenue Service (IRS) and individual state Departments of Revenue have ramped up digital tracking and enforcement, meaning the “head in the sand” approach no longer works.
At Sterlinx Global Ltd, we see many ambitious UK brands hit unnecessary roadblocks because they applied “UK logic” to a “US system.” To help you navigate this, we’ve outlined the seven most common mistakes UK sellers make with 2026 US tax compliance and, more importantly, how you can fix them before they cost you your margins.
1. The “I’m in the UK, so I don’t owe US Tax” Myth
The mistake: Many UK directors believe that because their company is registered in Companies House and they have no physical office in the US, they are outside the reach of the US taxman.
The reality: In 2026, physical borders matter less than digital footprints. If you sell to US customers, you are likely creating “Nexus”: a legal connection that gives a state the right to tax you. US authorities now use advanced data-sharing agreements with marketplaces and shipping carriers to identify high-volume overseas sellers.
The fix: Acknowledge that US tax obligations are based on where your customers are, not where your desk is. You must actively monitor your sales activity against the specific thresholds of each US state. Don’t wait for a “nexus discovery” letter; be proactive.
2. Misunderstanding the “Economic Nexus” Trigger
The mistake: UK sellers often think they only need to worry about tax if they have a warehouse or employees in America.
The reality: While physical presence is a trigger, Economic Nexus is the more common trap. Most states have a threshold: typically $100,000 in gross sales or 200 separate transactions within a calendar year. If you cross that line in a state like California or New York, you are legally required to register and collect sales tax.
The fix: Implement a tracking system that monitors your transaction count and revenue per state in real-time. Since 2026 regulations have tightened, even one dollar over the threshold can trigger back-dated liabilities. If you are unsure how to track this across 50 different jurisdictions, talk to an expert who can automate this for you.
3. Delaying Registration After Crossing the Threshold
The mistake: Thinking, “I’ll just wait until the end of the year to sort out my US taxes.”
The reality: US sales tax is not a “year-end” activity. Once you hit a nexus threshold, you are often required to register and start collecting tax within 30 to 60 days. If you continue selling without registering, you are effectively “stealing” the tax from the state. When you eventually do register, the state may demand the tax you should have collected out of your own pocket, plus hefty interest and penalties.
The fix: Register in each applicable state the moment you anticipate hitting the threshold. Keep in mind that as a UK resident, you may need a US Individual Taxpayer Identification Number (ITIN) or an Employer Identification Number (EIN) for your business. This process can take weeks, so start early.
4. Treating the US Like One Single Market
The mistake: Assuming US tax works like the UK, where there is one flat VAT rate and one central authority (HMRC).
The reality: The US has no national VAT. Instead, it has over 11,000 different local tax jurisdictions. Each of the 50 states has its own rules, filing frequencies (monthly, quarterly, or annual), and deadlines. Some states want your return by the 15th of the month; others by the 20th or 23rd. Missing a “zero return” (a filing where you owe $0) can still result in a $50–$100 penalty per state.
The fix: Stop viewing the US as one country for tax purposes. Treat it as 50 different countries. You need a dedicated tax calendar or a compliance partner like Sterlinx Global to manage these varying deadlines. Managing cross-border currency and finances is hard enough; don’t add manual tax tracking to your plate.
5. Confusing US Sales Tax with UK VAT
The mistake: Thinking that paying US Sales Tax exempts you from UK obligations, or vice versa.
The reality: These are two completely different beasts. UK VAT is a value-added tax collected at every stage of production. US Sales Tax is a consumption tax collected only at the final point of sale to the end-user. You can easily find yourself in a position where you owe both if you don’t structure your pricing and accounting correctly.
The fix: Maintain separate “buckets” for your UK and US accounting. Ensure your bookkeeping software is configured to handle US-style sales tax without messing up your UK tax tips and accounting. We recommend using a global compliance suite that handles both sides of the Atlantic simultaneously.
6. Neglecting Exemption Certificates
The mistake: Selling to a US wholesaler or another business and not charging sales tax because “it’s B2B.”
The reality: In the US, every sale is considered taxable unless you can prove otherwise. If you don’t collect sales tax from a buyer, you must have a valid, state-specific Exemption Certificate on file from them. During a state audit, if you can’t produce that certificate, the auditor will charge you the missing tax: even if the buyer was technically exempt.
The fix: Create a digital vault for all US exemption certificates. Before you ship a tax-free order to a US business, ensure you have their signed documentation. This simple habit can save you tens of thousands of dollars in an audit.
7. Blind Trust in “Marketplace Facilitator” Laws
The mistake: Thinking, “Amazon/eBay/Walmart collects the tax for me, so I don’t have to do anything.”
The reality: While Marketplace Facilitator laws have simplified things (where the marketplace collects and remits tax on your behalf), they don’t solve everything. You may still be required to register for a sales tax permit in states where you have nexus, even if the marketplace pays the tax. Furthermore, these laws often don’t cover your own Shopify store or direct website sales.
The fix: Verify your responsibility in writing with each platform. Even if they collect the tax, you might still have a “reporting-only” obligation. If you sell through multiple channels (e.g., Amazon + your own website), the complexity multiplies. Ensure your company formation and tax strategy account for this multi-channel reality.
How Sterlinx Global Solves the 2026 US Tax Puzzle
At Sterlinx Global Ltd, we don’t just offer “advice.” We provide a full-scale compliance engine. Our team handles the heavy lifting:
- Nexus Analysis: We scan your sales data and pinpoint exactly which states owe you tax obligations.
- Registration Management: We file your sales tax permits across all necessary states and manage renewals.
- Quarterly Compliance: We calculate, file, and remit your taxes on schedule, across all 11,000+ jurisdictions where you have nexus.
- Audit Defence: We keep digital records of exemption certificates and maintain bulletproof documentation to protect you in a state audit.
- Multi-Channel Support: Whether you sell on Amazon, eBay, Shopify, or your own website, we track it all and ensure nothing falls through the cracks.
The cost of compliance is always cheaper than the cost of non-compliance.
