For a US citizen leaving the UK, moving country does not end the US tax filing story. The practical job is to coordinate three timelines: the UK departure year, the US calendar tax year, and the tax rules in the new country.
Start by separating residence from citizenship. The UK uses residence tests to decide the scope of UK tax. The United States generally taxes US citizens and resident aliens on worldwide income even while they live abroad. Relief may be available, but it must be claimed and reported correctly.
First decision: when does UK residence change?
Use the Full UK Statutory Residence Test before assuming your UK tax position ends on the day of your flight. Enter expected UK days, UK workdays, accommodation and family ties, then compare alternative travel plans. It is a planning screen, not a legal residence determination, so take advice if a tie or workday is borderline.
Next use the Split-Year Planner if you leave partway through the UK tax year. It asks for the move, work and home facts that determine which HMRC case may apply. Split-year treatment can divide a qualifying year into UK and overseas parts, but it applies only in defined cases and does not change your US calendar-year filing period.
HMRC says a person who normally files Self Assessment generally reports departure using the residence pages, SA109. Someone who does not normally file may need form P85. Check HMRC's current tax guidance for people leaving the UK before filing.
Second decision: FEIE or Foreign Tax Credit?
These reliefs solve different problems.
The Foreign Earned Income Exclusion can exclude qualifying foreign earned income, subject to eligibility tests and an annual limit. For 2026, the IRS states that the maximum exclusion is $132,900 per qualifying person. It covers earned income, not pensions, investment income or every type of compensation.
Use the US FEIE Calculator when you expect to maintain a foreign tax home and may meet either the bona fide residence test or the physical presence test. Enter foreign earned income, housing and travel assumptions; it compares a planning estimate, not eligibility. The physical presence route generally requires at least 330 full days in foreign countries during a 12-month period. This makes travel dates important.
The Foreign Tax Credit may reduce US tax where foreign income tax is imposed on the same income. Use the US Foreign Tax Credit Calculator when you have actual or estimated UK and destination-country tax by income category. Use the same income assumptions as the FEIE comparison; the result is a comparison, not a Form 1116 calculation or treaty analysis.
Do not simply choose the larger-looking number. The IRS says you cannot claim a foreign tax credit for tax allocated to income excluded under FEIE. The election can also affect other credits and future returns. Read the current IRS pages on the Foreign Earned Income Exclusion and Foreign Tax Credit, then model both routes before filing.
What to gather for the comparison
- Salary, bonus, equity compensation and self-employment income by work location.
- UK tax paid or accrued and expected tax in the destination country.
- Exact travel days, including time spent in the United States.
- Housing costs and employer allowances.
- Passive income such as interest, dividends, rent and capital gains.
- Prior FEIE elections and unused foreign tax credit carryovers.
Third decision: which foreign accounts remain reportable?
Closing a UK current account after the move does not erase the period when it was open. FinCEN requires an FBAR where a US person has reportable foreign accounts whose aggregate value exceeds $10,000 at any time during the calendar year.
Use the FBAR Checker to inventory UK and other non-US accounts and test the aggregate threshold. Use maximum values, not year-end balances. Include accounts across countries rather than testing each bank separately. Confirm the filing rules on FinCEN's official FBAR page.
FBAR is separate from the income tax return. Form 8938 may also apply under different thresholds and definitions. If you hold a UK ISA, investment account, company, trust or pension, get US advice on classification and information returns before changing or liquidating it.
Do not overlook state tax
Federal tax residence is only part of the US picture. A move from the UK to the United States may establish residence in a state immediately. A move from the UK to a third country can still leave questions about a former US domicile, depending on the state's rules and your continuing connections.
Use the US State Tax Calculator when choosing where to return or when testing whether state tax materially changes the package. Use it early, before signing a lease, registering to vote, obtaining a driving licence or moving the centre of family life.
The calculator compares financial outcomes; it does not determine domicile. State residence rules vary, so high-income earners, business owners and people with equity compensation should obtain state-specific advice.
A worked example
Taylor, a US citizen, leaves London for Dubai on 30 September. Taylor keeps a UK savings account and ISA, receives a UK bonus in December for work performed partly in London, and expects two trips to the United States.
Taylor first runs the UK SRT and Split-Year Planner using the actual departure and return-visit schedule. For the US return, Taylor separates compensation by where the work was performed, then compares FEIE and Foreign Tax Credit outcomes. The FBAR Checker includes the maximum calendar-year values of every non-US account, including accounts closed after the move.
The result is not one “expat tax number”. It is a map of issues: UK departure residence, sourcing of the deferred bonus, eligibility for US relief, destination-country tax and foreign-account reporting. Taylor sends that map and the underlying documents to an adviser familiar with all three countries.
Your departure file
Keep one folder with:
- UK departure and destination arrival evidence.
- UK payslips, P45, P60 and Self Assessment records.
- Travel calendar and workday allocation.
- Tax payment evidence by country and income category.
- Highest annual balance for each non-US account.
- Equity award agreements and vesting schedules.
- Pension, ISA, company and trust documents.
- Prior US federal and state returns, Forms 1116 and 2555, and FBAR confirmations.
When to get professional advice
Get coordinated advice before the move if you hold a UK ISA or pooled investment fund, own more than a straightforward bank account and workplace pension, receive stock compensation, are self-employed, own a company, have not filed US returns or FBARs, or may be taxable in a US state.
Timing matters most when you can still change the departure date, travel pattern, bonus payment, asset sale or account structure. Do not liquidate an investment simply because it is awkward to report without first checking the UK, US and destination-country consequences.
Action order before you move
- Run the UK Statutory Residence Test with your planned days, work and ties; then test split-year treatment if you leave mid-year.
- Build a work-location and travel calendar, then compare FEIE and Foreign Tax Credit using the same income assumptions.
- Run the FBAR Checker from each account’s highest annual value, not its year-end balance.
- Take the departure file to a cross-border adviser before changing an ISA, investment, equity arrangement or business structure. Use premium multi-year planning only when several tax years or interacting decisions need an adviser-ready record of assumptions.
Leaving the UK is manageable when the departure date, income allocation and account reporting are kept in one file and tested in that order. The calculators make the decisions visible; the filings and any cross-border treatment still need to match your facts.