Next Tax Source ✦ Specialisms ✦ US & UK
US–UK Cross-Border · Founders & Companies

US–UK Cross-Border Business Tax

For founders and companies operating on both sides of the Atlantic. We structure your US and UK entities, keep the cross-border filings (Form 5471, 5472, permanent establishment, treaty) clean, and a licensed professional signs every return.

Request A Private Consultation Where To Base — US vs UK

The moment a business operates on both sides of the Atlantic, the filings multiply. A US founder who opens a UK company, or a UK founder who incorporates in Delaware to raise, quickly discovers that each country wants to tax the same profits and each has its own reporting the other does not. Handled early, it is a structure. Handled late, it is a penalty. We keep the US and UK sides of a company coherent — and signed.

The filing US owners of a foreign company most often miss is Form 5471 — its penalties start high and stack, and they keep your whole US return open until filed. If that is you, start there.

What We Handle

Who This Is For

The Traps We Are Asked To Fix

Cross-border business tax rarely goes wrong through evasion — it goes wrong through filings nobody knew existed. The recurring ones:

How Next Tax Source Handles It

Our specialist AI agents prepare the corporate returns, the cross-border information filings and the founders' own returns to a ready-to-sign standard with full workpapers. A licensed US CPA or Enrolled Agent and a UK chartered accountant review and sign their respective sides. Rates, thresholds and deadlines are set annually and change; we confirm the current figures against IRS, HMRC and official guidance before anything is prepared.

Deciding where to base in the first place? Model it with the US vs UK vs UAE calculator. Handling your personal expat filing too? See our US & UK expat tax accountant service.

Questions People Ask

I am a US citizen who opened a UK Ltd — what do I have to file?
Most US owners of a UK company must file Form 5471 with their US return, and often more besides. It is the filing people most commonly miss, its penalties start high and compound, and an unfiled 5471 keeps your entire US return open to the IRS until it is filed. We identify exactly which category applies to you and prepare it as part of your US filing.
What is permanent establishment and when does it catch my company?
A permanent establishment (PE) is a taxable business presence in a country — created by things like staff, an office, held stock or the authority to conclude contracts there. If your US company creates a PE in the UK (or vice versa), that country can tax the profits attributable to it, and a return is due. We assess PE risk before it becomes an unplanned filing.
How do the US and UK avoid taxing my company's profits twice?
Through the US–UK tax treaty and double-taxation relief, applied in the right order. Structured and documented correctly, profits are taxed once and credited across, not taxed twice. Getting the treaty positions and the sequencing right is the core of cross-border business tax work.
Do I need transfer pricing documentation for a small US–UK group?
If related US and UK entities charge each other — management fees, IP, services, loans — those charges need a defensible arm's-length basis, and the documentation should be proportionate to the size of the group. Small groups do not need enterprise-scale files, but they do need a coherent basis that stands up if questioned.
Should I incorporate in the US or the UK?
It depends on where your customers, investors and team are, and on your own tax position — a US Delaware C-corp is what most US VCs expect, while a UK Ltd may suit a UK-centred business. Model the tax side with our US vs UK vs UAE calculator, then talk to us about the investor and structuring factors a rate comparison alone will miss.
Who prepares and who signs?
Our specialist AI agents prepare the corporate and cross-border filings to a ready-to-sign standard with complete workpapers. A licensed US CPA or Enrolled Agent signs the US filings and a UK chartered accountant signs the UK filings. The company's officers sign and submit; we never file to a tax authority on your behalf.

Every Filing, Signed By A Professional

We prepare it all to a ready-to-sign standard; a US CPA or Enrolled Agent and a UK chartered accountant review and sign before anything is filed. Tell us your situation and we'll return a scoped proposal within one business day.

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