With the 15 April deadline now behind us, the IRS is shifting from deadline pressure to compliance follow-up. The latest Internal Revenue Bulletin, IRS Bulletin 2026-16, released this week, includes the 2025 APMA Program report. That matters if your UK business has a US subsidiary and you need to manage transfer pricing properly through Advance Pricing Agreements.
At Sterlinx Global, we see this pattern every year. Once Tax Day passes, many businesses assume the pressure is over. It is not. This is when late payment penalties, missed filings, and cross-border reporting issues start to become expensive. If you trade in the US, this is the moment to tighten up your records, clear any open liabilities, and make sure your federal and state compliance position is under control.
Use the Post-Deadline Window to Fix Problems Fast
The biggest mistake after Tax Day is doing nothing. If you missed the payment deadline, the IRS failure-to-pay penalty is generally 0.5% of the unpaid tax per month, capped at 25%. Interest also continues to build. That means waiting costs you money every month the balance remains open.
Don't worry, there is still a smart next step. If you have not filed yet, filing for an extension can still help reduce exposure to the separate failure-to-file penalty, which is generally 5% per month on unpaid tax, also subject to its own cap and interaction rules. An extension does not delay payment, but it can reduce how much the filing side of the penalty problem grows. This is why acting quickly still matters, even after 15 April.
Watch APMA Developments if You Have US Group Entities
The headline item in IRS Bulletin 2026-16 is the publication of the 2025 APMA Program report. APMA stands for Advance Pricing and Mutual Agreement. In simple terms, it is the part of the IRS that handles Advance Pricing Agreements and competent authority matters linked to transfer pricing.
If your UK company operates through a US subsidiary, this is not background noise. It is a signal. The report gives useful insight into how the IRS is handling pricing disputes, bilateral agreements, and cross-border transfer pricing administration. You do not need to become a transfer pricing specialist overnight, but you do need clean intercompany records, consistent pricing support, and proper filing discipline. That will save you time if the IRS ever asks questions.
Clear Federal and State Liabilities Before They Snowball
Federal tax is only part of the picture. If you also owe state taxes, you need to deal with those fast as well. States apply their own penalties and interest rules, and these can continue running even if you are focused only on the IRS balance.
This is especially important in active trading states such as Illinois, where many international businesses create sales tax, payroll, or income tax touchpoints. Settle any confirmed state liabilities as soon as possible to stop the interest clock from running longer than necessary. If you are unsure what is outstanding, reconcile your filings against your platform data, payment records, and state notices now rather than later.
Take These Late Payment Steps Now
If you are behind, keep it simple and move in order:
- File the return or extension immediately. Doing this can reduce exposure to the higher failure-to-file penalty.
- Pay as much as you can now. Partial payment still helps cut the monthly failure-to-pay penalty and interest.
- Check for state balances separately. Federal and state liabilities do not resolve each other.
- Review intercompany transactions. If you have a US subsidiary, make sure transfer pricing support and cross-border records are up to date.
- Keep notices and confirmations organised. You will save time if the IRS or a state authority follows up.
This is where a structured compliance process makes a difference. You provide the data, and we keep the filings, calculations, and reconciliations moving so small issues do not turn into expensive ones.
Understand the US-UK Tax Treaty (And Its Limits)
Many UK business owners assume the US-UK Income Tax Treaty solves all their problems. While the treaty is a fantastic tool to prevent double taxation, it does not exempt you from filing requirements. You may still need to file a US tax return to claim the treaty benefits.
Furthermore, the treaty generally covers federal income tax, not state-level sales tax or franchise taxes. You could be exempt from federal tax but still owe thousands in state taxes. Keeping a pulse on daily updates helps you distinguish between treaty-protected income and state-level obligations.
5 Practical Moves After Tax Day
Use this checklist to get back in control:
- File now, even if you cannot pay in full. This helps limit the more severe filing penalty.
- Pay down the balance fast. Every payment reduces future penalties and interest.
- Reconcile state exposure. Check states where you have sales, payroll, staff, inventory, or marketplace activity.
- Review transfer pricing positions. If you have a UK-US group structure, keep intercompany documentation tidy and consistent.
- Get ongoing compliance support. Post-deadline clean-up is easier when your bookkeeping and filings are already structured.
Why UK Businesses Trust Sterlinx Global
Managing cross-border tax is a full-time job. You should be focusing on scaling your brand, not reading IRS bulletins at 2 AM. Sterlinx Global provides an end-to-end compliance delivery system. We handle the heavy lifting: from Sales Tax filings in various US states to managing cross-border VAT for your European operations.
Our model is simple: you provide the transaction data, and we ensure your filings are accurate, timely, and compliant with the latest laws. Whether you need a full-suite accounting solution or modular help with US Sales Tax, we have the infrastructure to support your growth.
Frequently Asked Questions
What is the IRS failure-to-pay penalty after 15 April?
It is generally 0.5% of the unpaid tax per month, up to a maximum of 25%, plus interest.
Should I still file an extension if I missed the payment deadline?
Yes, if you have not filed yet. An extension does not delay the tax due, but it can help reduce exposure to the separate failure-to-file penalty, which is generally much higher.
Why does IRS Bulletin 2026-16 matter to UK businesses?
It includes the 2025 APMA Program report, which is relevant for UK groups with US subsidiaries that need to manage transfer pricing and Advance Pricing Agreements properly.
Do I need to deal with state tax liabilities separately?
Yes. State tax balances, penalties, and interest are separate from your IRS account. You need to review and settle them individually.
What should I do first if I am late?
File the return or extension, pay what you can immediately, then review any state balances and cross-border reporting gaps.
Don't Let a Missed Deadline Turn Into a Bigger Problem
Post-Tax Day is when fast action matters most. If you have unpaid federal tax, unresolved state balances, or a UK-US group structure that raises transfer pricing questions, now is the time to get organised. We help you stay compliant with ongoing bookkeeping, tax calculations, filings, and practical follow-through so issues are handled before they escalate.
Talk to an expert at Sterlinx Global today if you need help clearing late tax issues and keeping your US compliance on track.
