Cross-border tax filing across two systems
Looking for expert support with cross-border tax filing in the UK and US? As US UK Tax Experts, we help expats, dual citizens, and internationally mobile professionals meet complex tax obligations across both jurisdictions. Our team of dual-qualified tax accountants in London ensures seamless dual tax compliance, correct use of the US-UK tax treaty, and returns that keep your income, pensions, and investments from being taxed twice.
Why It’s Important to Have Specialist Cross-Border Tax Experts
Managing tax across the US and UK is far more complex than standard accounting. The two systems operate under different rules, deadlines, and reporting requirements, and without the right expertise, it's easy to face double taxation, missed reliefs, or penalties from the IRS and HMRC.
By working with specialist cross-border tax accountants, you gain access to professionals who understand both jurisdictions in detail. We coordinate dual tax compliance in London, apply the US-UK tax treaty on the returns themselves, and claim the credits and reliefs that keep your income, pensions, and investments from being taxed twice.
Every expat, dual citizen, and internationally mobile professional has unique circumstances. Only dedicated specialists can prepare both sets of returns so that they agree with each other and every relief is claimed in the right country.
The numbers behind why this sits awkwardly between two systems.
How an engagement runs
Two authorities, one file. Here is what working together actually looks like.
- Review
We look at both sides together: what you file, where, and what has already been filed or missed.
- Position
We set out the treaty position and reliefs that apply to you, with the numbers behind each option.
- File
We prepare and submit to the IRS and HMRC, keeping the two sets of filings consistent with each other.
- Keep current
Two tax calendars means deadlines all year. We track them and tell you before they arrive.
What is included
The filings this service covers on both sides of the Atlantic.
Questions we are asked most
The ones that come up in almost every first conversation about this.
Mostly by allocating taxing rights between the two countries and then giving credit for tax paid in the other. It does not stop the US taxing its citizens, so for Americans in the UK the practical mechanism is usually credits rather than exemption.
When both countries consider you resident, the treaty applies tests in sequence, permanent home, then centre of vital interests, then habitual abode, then nationality, to settle which country treats you as resident. It matters most in the year you move.
The year of a move is often a split year on the UK side, and for US citizens a full-year US return still runs alongside it. The dates of departure and arrival, and of any asset sale around them, decide which country taxes what, so they have to be recorded accurately and reported the same way on both returns.
Generally the treaty prevents the US taxing growth inside a UK pension before it is drawn, and gives relief on the way out, but the reporting still has to be done and the protection is not automatic. Employer schemes and personal ones are not always treated alike.
The country with taxing rights depends on the asset and your residence, and the two systems calculate gains differently, notably on currency movement and on relief for a main residence. It is common for a disposal to be tax free in one country and taxable in the other.
Let's get both sides right
Tell us your situation and we will map out exactly what you owe, where, and when.