Split-Year Tax Treatment US Expat UK Guide |

Introduction

You arrived in the UK in September 2025 to take up a new role in London — partway through the UK tax year that runs 6 April 2025 to 5 April 2026. Your UK accountant has mentioned "split-year treatment," but you are not sure how it applies to your specific arrival circumstances. Your US tax CPA has mentioned "dual-status year" filing for your 2025 US Form 1040, but the two frameworks operate independently in conversation. The integrated split-year tax treatment US expat UK evaluation operates across both the UK-side RDR3 framework (eight specific cases for splitting UK tax years) and the US-side Form 1040 dual-status year framework under IRC Section 7701(b)(2)(C) — proper integrated specialist coordination produces materially better positioning than generic preparation by separate UK-only and US-only providers.

This guide is written for US citizens and US tax-resident filers arriving in the UK mid-UK-tax-year, US expats leaving the UK mid-UK-tax-year, US-UK dual citizens with mid-year residency changes, Green Card holders relocating to or from the UK partway through the UK tax year, and any US client requiring specialist evaluation of integrated UK split-year and US dual-status year coordination. By the end, you will know exactly how split-year tax treatment for US expats in the UK operates in 2026. For our broader US-UK service overview, see our US-UK cross-border tax advisory service.

What Is Split-Year Tax Treatment for US Expat UK Evaluation

Split-year tax treatment US expat UK evaluation refers to specialist analysis of the UK split-year treatment framework under HMRC RDR3 guidance (the HMRC manual covering the UK Statutory Residence Test, including split-year rules), integrated with the US-side Form 1040 dual-status year framework for US expats arriving in or leaving the UK partway through a UK tax year. The HMRC RDR3 reference sits at https://www.gov.uk/government/publications/rdr3-statutory-residence-test-srt.

The UK split-year framework under FA 2013, Schedule 45, Part 3 (the UK Statutory Residence Test legislation), operates through eight specific cases. Cases 1-3 cover UK tax year departure scenarios — Case 1 (starting full-time work overseas), Case 2 (partner of someone starting full-time work overseas), Case 3 (ceasing to have a UK home). Cases 4-8 cover UK tax year arrival scenarios — Case 4 (starting to have only a home in the UK), Case 5 (starting full-time work in the UK), Case 6 (ceasing full-time work overseas), Case 7 (partner of someone ceasing full-time work overseas), Case 8 (starting to have a UK home).

The substantive eligibility analysis for each case requires the filer to be a UK tax resident for the relevant UK tax year under the standard UK Statutory Residence Test, plus to satisfy the specific conditions for the relevant case (typically including residence pattern, employment pattern, home arrangement, and timing requirements). Where the eligibility conditions are satisfied, the UK tax year is split into a UK-resident portion (subject to UK tax on worldwide income and gains during that portion, as applicable) and a UK non-resident portion (subject to UK tax only on UK-source income and gains during that portion).

The US-side dual-status year framework under IRC Section 7701(b)(2)(C) and Treas. Reg. 1.871-13 operates in parallel to the UK split-year framework for US expats. A dual-status year on the US side typically arises where the filer transitions between US tax resident (US citizen always remains US tax resident under IRC Section 1; Green Card holder is US tax resident under IRC Section 7701(b)(1)(A); substantial presence test resident under IRC Section 7701(b)(1)(A)) and US non-resident alien status partway through a US calendar tax year.

For US-citizen filers arriving in or leaving the UK partway through a UK tax year, the US-side framework typically does NOT produce a dual-status year — US citizens remain US tax residents on a worldwide income basis under IRC Section 1, regardless of UK residence pattern. The dual-status year framework typically applies only when the filer transitions to or from US tax residence (e.g., a Green Card status change or a substantial presence test threshold crossing).

The integrated split-year tax treatment US expat UK evaluation operates across UK-side RDR3 case selection plus optimal UK Self Assessment positioning for the split-year, US-side Form 1040 positioning (typically not dual-status for US citizens but with substantive Form 1116 Foreign Tax Credit positioning across the UK-resident and UK non-resident portions of the UK tax year intersecting with the US calendar tax year), and integrated annual workflow design. The IRS dual-status reference sits at https://www.irs.gov/individuals/international-taxpayers/dual-status-aliens.

This matters in 2026 because the post-April 2025 UK Foreign Income and Gains regime under Finance Act 2025 interacts with the split-year framework for qualifying arrivals — the 4-year UK FIG regime exemption period begins from the UK arrival tax year, potentially producing materially different substantive UK tax positioning, the integrated US-UK coordination requires specialist depth on both UK split-year cases and US-side dual-status year framework, and many US-UK relocations occur mid-UK-tax-year, producing split-year scenarios for nearly all US expats arriving or leaving the UK outside the 6 April annual cycle. The HMRC reference sits at https://www.gov.uk/.

The real consequences of inadequate split-year tax treatment US expat UK evaluation, include suboptimal RDR3 case selection producing a larger UK-resident portion than necessary, missed UK FIG regime claim timing for qualifying arrivals, suboptimal Form 1116 Foreign Tax Credit positioning across the UK-resident and UK non-resident portions, missed dual-status year filing where applicable on the US side, and integrated US-UK positioning gaps producing materially adverse combined US-UK tax outcome.

Why Split-Year Tax Treatment US Expat UK Evaluation Matters More Than Ever in 2026

The split-year tax treatment of US expats in the UK evaluation matters materially in 2026 for several distinct reasons. First, the post-April 2025 UK Foreign Income and Gains regime under the Finance Act 2025 interacts with the split-year framework for qualifying arrivals. Qualifying UK arrivers (UK residents in the current tax year with at least 10 consecutive prior UK non-residence tax years) benefit from the 4-year UK tax exemption on foreign income and foreign gains starting from the UK arrival tax year — the integrated split-year plus UK FIG regime positioning materially affects the substantive UK tax outcome for the arrival year. You can read our broader guidance on our US-UK cross-border tax planning service.

Second, the post-April 2025 UK domicile reforms under the Finance Act 2025 replaced the historic non-domicile framework — the integrated arrival-year planning for US expats incorporates the new Long-Term UK Resident (LTUKR) framework alongside split-year case selection.

Third, the TCJA sunset on 1 January 2026 reduced the US lifetime gift and estate exemption from $13.99 million per person (2025) to approximately $7 million per person (2026 indexed) — UK arrival year planning for high-net-worth US filers incorporates the integrated US estate planning consideration alongside the substantive UK split-year and UK FIG regime positioning. The IRS reference sits at https://www.irs.gov/.

Fourth, the September 2025 US-UK FATCA Intergovernmental Agreement data feed transmitted approximately 2.4 million US-person UK account records, advancing IRS automated detection. Proper, integrated US-UK arrival-year compliance from the outset is materially important to avoid future remediation requirements.

Core Section: The UK Split-Year Framework Cases 1 Through 8

Cases 1-3: UK departure scenarios

Case 1 applies to UK tax-resident filers who leave the UK to start full-time work overseas, with the split-year applying from the start of the overseas employment. The substantive eligibility requires the filer to be UK resident for the relevant UK tax year, to start full-time work overseas during the UK tax year, to satisfy the overseas work test (working more than 35 hours per week on average overseas, with no significant break from overseas work), and to satisfy the limited UK days condition (typically below 90-91 UK days during the post-departure portion of the UK tax year). The HMRC RDR3 reference sits at https://www.gov.uk/government/publications/rdr3-statutory-residence-test-srt.

Case 2 applies to the partner of someone qualifying under Case 1 — the partner can split the UK tax year aligned with the Case 1 partner's overseas departure, where the partner accompanies the Case 1 individual overseas and otherwise satisfies the conditions.

Case 3 applies to UK tax-resident filers who cease to have a UK home during the UK tax year, producing a split-year application from the date of UK home cessation. The substantive eligibility requires the filer to have a UK home at the start of the UK tax year, to cease having a UK home during the UK tax year, to spend fewer than 16 UK days during the post-cessation portion of the UK tax year, and to be UK non-resident for the following UK tax year.

Cases 4-8: UK arrival scenarios

Case 4 applies to UK arrivals who have only a UK home (no overseas home retained), resulting in a split-year application from the date of UK home establishment. The substantive eligibility requires the filer to be a UK non-resident for the prior UK tax year, to start to have a UK home during the UK tax year, to have only a UK home (no overseas home retained), to meet the UK home conditions for at least 30 consecutive days, and to be a UK resident for the following UK tax year.

Case 5 applies to UK arrivals who start full-time work in the UK, and they must submit a split-year application from the start of that work. The substantive eligibility requires the filer to be UK non-resident for the prior UK tax year, to start full-time work in the UK during the UK tax year, to satisfy the UK full-time work conditions (working more than 35 hours per week on average in the UK for at least 365 days starting in the UK tax year, no significant break), and to be UK resident for the following UK tax year.

Case 6 applies to UK arrivals who cease full-time work overseas — a typical scenario for filers returning to the UK from prior overseas employment. The substantive eligibility requires the filer to have been a UK non-resident for the prior UK tax year following the Cathe se 1 split-year departure (or similar pattern), to have ceased full-time work overseas during the UK tax year, and to have been a UK resident for the following UK tax year.

Case 7 applies to the partner of someone qualifying under Case 6 — the partner returning to the UK with the Case 6 individual.

Case 8 applies to UK arrivals who begin to have a UK home, resulting in a split-year application from the date of UK home establishment. The substantive eligibility requires the filer to be UK non-resident for the prior UK tax year, to start to have a UK home during the UK tax year, to have a UK home for the remainder of the UK tax year and continuing into the following UK tax year, to be UK resident for the following UK tax year, and to satisfy the UK days conditions during the pre-arrival portion of the UK tax year.

Case selection methodology for US expat arrivals

For US expat arrivals to the UK, the substantive case selection typically considers Cases 4, 5, and 8 as the principal arrival scenarios. Case 5 (UK full-time work) is the most common case for US expats arriving on UK employment-based relocation — providing a split-year application from the start of UK full-time work, which is typically the relocation date or shortly thereafter. Case 8 (starting to have a UK home) provides an alternative split-year application from a UK home establishment, which may result in an earlier split-year application than Case 5, where the US expat establishes a UK home before UK employment commences. Case 4 (starting to have only a UK home) requires no overseas home retention, which is materially limiting for US expats who typically retain US-domiciled property — applicability depends on the specific US property and home positioning.

The substantive case selection requires specialist evaluation of the specific arrival circumstances, including the UK employment start date, the UK home establishment date, the US home retention or disposal pattern, and the integrated UK-US arrival year timing. Optimal case selection typically produces the earliest practical split-year application, minimizing the UK-resident portion of the UK arrival tax year.

How US Expats Apply Integrated Split-Year and Dual-Status Year Coordination

The first step is the comprehensive arrival or departure diagnostic. The specialist documents the US expat's US citizenship and US tax residency positioning, UK residency positioning under the UK Statutory Residence Test for the relevant UK tax years, the specific arrival or departure timing (UK arrival date, UK employment start date, UK home establishment date, US home retention or disposal, US employment end date), and the integrated US-UK calendar alignment.

The second step is the UK RDR3 case selection analysis. The specialist evaluates the eight cases (Cases 1-3 for departure scenarios, Cases 4-8 for arrival scenarios) against the specific arrival or departure circumstances, identifies the applicable case (or cases where multiple cases apply with substantive choice opportunity), and documents the optimal case selection with supporting evidence. The HMRC RDR3 reference sits at https://www.gov.uk/government/publications/rdr3-statutory-residence-test-srt.

The third step is the documentation for the UK split-year application. The specialist prepares the UK Self Assessment for the relevant UK tax year, applying the selected RDR3 case and properly treating the UK-resident and UK non-resident portions. The substantive UK Self Assessment positioning operates with UK PAYE on UK employment income during the UK-resident portion, UK Self Assessment for any UK-source income during the UK non-resident portion, UK FIG regime claim for qualifying arrivals, where applicable, and integrated treatment of all UK tax events.

The fourth step is the US-side Form 1040 positioning analysis. For US citizens, the US-side framework operates as standard US worldwide taxation on Form 1040 — typically, no dual-status year filing applies (US citizens remain US tax residents throughout the calendar year, regardless of UK residence pattern). For Green Card holders, the analysis may produce a dual-status year filing when Green Card status changes during the US calendar tax year. For a substantial presence test of US residents, the analysis may result in a dual-status year filing if the substantial presence threshold is met during the year.

The fifth step is the integrated Form 1116 Foreign Tax Credit positioning across the UK-resident and UK non-resident portions of the UK tax year, intersecting with the US calendar tax year. The substantive analysis operates with Form 1116 FTC available on UK Income Tax paid during the UK-resident portion of the UK tax year (UK Income Tax substantially exceeds US tax on UK salary producing substantial Form 1116 FTC) and limited or no Form 1116 FTC during the UK non-resident portion (where no UK tax is paid on the relevant income). The IRS Form 1116 reference is part of the broader Form 1040 framework.

The sixth step is the integrated US-UK arrival-year planning and execution. The post-arrival workflow integrates the UK split-year application, UK FIG regime claim where applicable, US Form 1040 with full Form 1116 FTC positioning, Form 8833 treaty election under Article 18(5) on any UK workplace pension or SIPP established during the arrival year, Form 8621 PFIC analysis on any UK ISA or UK SIPP fund holdings, Form 8938 FATCA where the relevant thresholds are met, FBAR via FinCEN BSA E-Filing on any UK accounts exceeding $10,000 aggregate peak during the calendar year, and any other applicable US-side and UK-side compliance.

The seventh step is the ongoing post-arrival integrated annual workflow establishment. The post-arrival ongoing engagement covers each subsequent UK tax year under the standard UK arising basis or UK FIG regime continuation (for qualifying arrivals within the 4-year exemption window), each US calendar tax year under the standard US worldwide taxation framework with Form 1116 FTC positioning, and integrated US-UK coordination.

Real-World Example — Split-Year Tax Treatment US Expat UK in Practice

Case Study: A US Citizen Arriving in London Mid-UK-Tax-Year With Integrated Split-Year and US Dual-Status Coordination

Jennifer is a US citizen, aged 38, formerly a resident of Boston, and currently a Senior Product Manager at a Boston-based technology company. In August 2025, Jennifer accepted a role at a London-based fintech company with an employment start date of 1 September 2025 — partway through the 2025-26 UK tax year running 6 April 2025 to 5 April 2026. Jennifer relocated from Boston to London in late August 2025, establishing a UK home in a rented Marylebone flat from 25 August 2025. Jennifer sold her Boston apartment in July 2025 (no US home retained). Jennifer's UK employment salary is £125,000, plus a £25,000 annual performance bonus. She is single with no children.

Jennifer's pre-arrival US financial position included a Charles Schwab US brokerage worth $385,000, a Fidelity 401(k) from her Boston employer worth $245,000, and a Vanguard US IRA worth $85,000. Jennifer had been a continuous US resident since 2009 (over 10 consecutive years of US residence without UK residence).

Jennifer's UK residence history: zero UK residence from any prior period — Jennifer had visited London on five short business trips between 2016 and 2024, totaling approximately 32 days, but had never been UK tax resident under the UK Statutory Residence Test. Jennifer had never claimed UK split-year treatment in any prior UK tax year.

In November 2025, Jennifer engaged US-UK Tax for comprehensive split-year tax treatment, a US expat UK evaluation covering her UK arrival year positioning.

The US-UK Tax Diagnostic identified the substantive integrated framework.

The UK Statutory Residence Test analysis for the 2025-26 UK tax year confirmed Jennifer's UK tax residence based on the UK ties test (Jennifer satisfied multiple UK ties tests, producing UK residence under the SRT, given her UK employment from 1 September 2025 onwards). The 2025-26 UK tax year was a UK arrival tax year for Jennifer, with split-year treatment evaluation applicable.

The RDR3 case selection analysis evaluated the applicable arrival cases. Case 5 (starting full-time work in the UK) was the principal applicable case — Jennifer started full-time work in the UK on 1 September 2025, satisfied the UK full-time work conditions (working more than 35 hours per week on average in the UK from 1 September 2025 onwards), and would be a UK resident for the following 2026-27 UK tax year. The split-year application under Case 5 produced UK-resident treatment from 1 September 2025 (UK employment start date) through 5 April 2026 (UK tax year-end) — approximately 217 days of UK-resident treatment. Case 8 (starting to have a UK home) was an alternative applicable case — Jennifer established a UK home on 25 August 2025, producing a UK-resident treatment from approximately 25 August 2025 onwards (223 days of UK-resident portion). Case 4 was not applicable — Jennifer had retained the US home until July 2025 disposal, but the case requirements were not clearly met.

The optimal case selection was Case 5, producing a slightly later split-year application date (1 September 2025 versus 25 August 2025), corresponding to approximately 6 fewer UK-resident days. The substantive case 5 selection was documented on the UK Self Assessment for the 2025-26 UK tax year.

The post-April 2025 UK Foreign Income and Gains regime analysis confirmed Jennifer's eligibility. Jennifer had at least 10 consecutive prior UK non-residence tax years (Jennifer had been continuously non-UK-resident from 2014-15 through 2024-25, totaling over 10 consecutive years satisfying the threshold). The UK FIG regime applied to Jennifer's 2025-26 UK arrival tax year as Year 1 of the 4-year exemption window, continuing through 2026-27 (Year 2), 2027-28 (Year 3), and 2028-29 (Year 4 ending 5 April 2029).

The UK FIG regime's substantive application resulted in UK tax exemptions on Jennifer's foreign income during the 4-year window. Foreign income (US dividend income from her Charles Schwab US brokerage, US partnership distributions, US-source interest income, any other non-UK source income) was UK-exempt during the 4-year window. Foreign gains (US capital gains on Charles Schwab US brokerage disposals during the 4-year window) were UK-exempt during the 4-year window. UK-source income (Jennifer's UK salary from the London-based fintech employer) was subject to UK Income Tax on a standard UK arising basis during the UK-resident portion of the 2025-26 UK tax year (from 1 September 2025 onwards under Case 5 split-year application).

The US-side Form 1040 positioning analysis confirmed Jennifer would file a standard Form 1040 (not dual-status year filing) — Jennifer is a US citizen and remains a US tax resident throughout the 2025 US calendar tax year under IRC Section 1, regardless of her UK arrival timing. The 2025 US Form 1040 (filed by 15 June 2026, expat automatic extension deadline) would include Jennifer's worldwide income for the full 2025 calendar tax year.

The integrated Form 1116 Foreign Tax Credit positioning was developed across the 2025 US calendar tax year. The UK-resident portion of the 2025-26 UK tax year (1 September 2025 onwards under Case 5 split-year application) intersected with the September-December 2025 portion of the 2025 US calendar tax year. UK Income Tax paid on Jennifer's UK salary from September-December 2025 (approximately £8,800 on £32,500 of UK salary in that period) flowed through Form 1116 FTC general category, producing approximately $11,500 USD-equivalent Form 1116 FTC available against US tax on the same UK salary. The Form 1116 FTC absorbed the US tax on the UK salary, with modest carry-forward.

The remaining 2025 US calendar tax year income (Jennifer's Boston-based salary from January-August 2025 at approximately $98,000 of US-source income plus US dividend income on her US brokerage continuing throughout 2025) was taxed on the standard US framework with no UK tax credit (UK source / UK tax did not apply to Jennifer's pre-September 2025 US-source income).

The Form 8938 FATCA analysis for the 2025 tax year confirmed that Jennifer's combined UK and US accounts exceeded the single UK-resident threshold ($200,000/$300,000) by year-end 2025 — Form 8938 was filed with the 2025 Form 104, disclosing all UK and US accounts above the applicable thresholds.

The FBAR via FinCEN BSA E-Filing analysis confirmed that Jennifer's UK account (a newly opened Lloyds London current account opened in September 2025) exceeded the $10,000 aggregate peak threshold by year-end 2025. The 2025 calendar year FBAR was filed via the FinCEN BSA E-Filing System by the extension deadline of 15 October 2026.

The Form 8833 treaty election was filed for the London-based fintech's workplace pension under Article 18(5) — Jennifer joined the UK workplace pension scheme automatically upon commencing UK employment.

The integrated UK-US annual workflow has been established. The 2026-27 UK tax year (full UK tax year) operated under the continuing UK FIG regime claim (Year 2 of a 4-year window). The 2026 US calendar tax year would operate as a full US tax year with Jennifer's UK salary subject to full UK Income Tax flowing through Form 1116 FTC, plus continuing US-side compliance.

The total US-UK Tax engagement scope covered the comprehensive arrival year evaluation and integrated planning at approximately £8,500 fixed fee covering split-year case selection analysis, UK FIG regime claim establishment, UK Self Assessment for 2025-26 UK tax year, 2025 US Form 1040 with Form 1116 FTC positioning, Form 8938 FATCA, FBAR, Form 8833 treaty election, and integrated US-UK arrival year coordination. The annual integrated workflow fee will be £4,200, effective immediately, covering ongoing UK and US compliance.

The outcome was comprehensive integrated US-UK arrival year positioning with optimal Case 5 split-year application minimising the UK-resident portion of the 2025-26 UK tax year, UK FIG regime claim established producing 4-year exemption on Jennifer's substantial US-source dividend income and capital gains (projected exemption value approximately $35,000-$55,000 USD-equivalent across the 4-year window depending on US asset performance), Form 1116 FTC carryforward establishment of approximately $4,500 from the partial-year 2025 UK Income Tax exceeding US tax on UK salary, integrated US-side Form 1040 with full compliance across Form 8938 FATCA, FBAR, Form 8833 treaty election, and going-forward integrated annual workflow established. The case study illustrates the split-year tax treatment in practical operation — the integrated framework across UK RDR3 case selection, UK FIG regime claim coordination, and US-side Form 1040 with Form 1116 FTC positioning produces a materially better outcome than generic preparation by separate UK-only and US-only providers.

Common Mistakes People Make With Split-Year Tax Treatment: US Expat, UK

The first mistake is failing to claim split-year treatment under RDR3, resulting in full-year UK tax residence on worldwide income from the start of the UK tax year. UK arrival-year filers without specialist split-year coordination frequently default to full-year UK tax residence status, resulting in material additional UK tax exposure on the pre-arrival portion of the UK tax year. The HMRC RDR3 reference is available at https://www.gov.uk/government/publications/rdr3-statutory-residence-test-srt.

The second mistake is the suboptimal selection of RDR3 cases. The eight cases under FA 2013 Schedule 45 Part 3 operate with substantively different timing, producing different UK-resident portion lengths for the arrival or departure year. Suboptimal case selection results in a larger UK-resident portion than necessary, thereby increasing UK tax exposure in the arrival or departure year.

The third mistake is failing to evaluate the UK FIG regime eligibility for qualifying arrivals. The post-April 2025 UK Foreign Income and Gains regime under the Finance Act 2025 provides a 4-year UK tax exemption on foreign income and foreign gains for qualifying arrivals (UK residents in the current tax year with at least 10 consecutive prior UK non-residence tax years). The integrated arrival-year planning should evaluate UK FIG regime eligibility alongside split-year case selection.

The fourth mistake is filing a US Form 1040 as a dual-status year for US citizens arriving in or leaving the UK. US citizens remain US tax residents on a worldwide income basis under IRC Section 1, regardless of UK residence pattern — dual-status year filing is typically not applicable for US citizens. The dual-status year framework under IRC Section 7701(b)(2)(C) and Treas Reg 1.871-13 primarily applies to Green Card status changes and substantial presence test threshold crossings, rather than to UK arrival or departure. The IRS dual-status reference sits at https://www.irs.gov/individuals/international-taxpayers/dual-status-aliens.

The fifth mistake is suboptimal Form 1116 Foreign Tax Credit positioning across the UK-resident and UK non-resident portions. The substantive Form 1116 FTC analysis applies to UK Income Tax paid during the UK-resident portion of the UK tax year that intersects with the US calendar tax year — specialist coordination produces optimal FTC positioning with carryforward management under IRC Section 904(c). Generic preparation frequently uses the Form 2555 Foreign Earned Income Exclusion rather than Forms 11 or 16r 16, resulting in a material, substantial position for higher-rate UK earners.

The sixth mistake is engaging UK-only or US-only specialists for the integrated arrival or departure year evaluation. The substantive split-year and US-side coordination require specialist depth in both the UK RDR3 and US Form 1040 frameworks — UK-only and US-only specialists typically lack the integrated cross-border depth required for substantive arrival-- or departure-year planning.

How US-UK Tax Can Help You With Split-Year Tax Treatment, US Expat UK

US-UK Tax is a specialist US-UK cross-border advisory firm with comprehensive expertise on the UK split-year framework under HMRC RDR3 guidance and the integrated US-side Form 1040 framework for US expats arriving in or leaving the UK partway through a UK tax year. Our team holds UK Chartered Tax Adviser (CTA) credentials under the Chartered Institute of Taxation, supporting UK Self Assessment and HMRC compliance with substantive UK Statutory Residence Test and split-year expertise, US IRS Enrolled Agent (EA) credentials supporting substantive US Form 1040 preparation and IRS representation, and integrated cross-border specialist expertise across both jurisdictions simultaneously. The CIOT reference sits at https://www.tax.org.uk/.

For US expat arrival or departure year clients we deliver comprehensive integrated split-year tax treatment US expat UK engagement including comprehensive arrival or departure diagnostic, UK Statutory Residence Test analysis under FA 2013 Schedule 45, UK RDR3 case selection analysis across Cases 1-8 with optimal case identification, UK split-year application documentation on UK Self Assessment for the relevant UK tax year, post-April 2025 UK Foreign Income and Gains regime eligibility evaluation and claim coordination for qualifying arrivers, post-April 2025 UK Long-Term UK Resident framework analysis, US-side Form 1040 positioning (typically standard US worldwide taxation for US citizens or dual-status year filing where applicable for Green Card holders or substantial presence test residents), integrated Form 1116 Foreign Tax Credit positioning across UK-resident and UK non-resident portions of the UK tax year intersecting with the US calendar tax year, Form 8833 treaty election under Article 18(5) on UK workplace pensions and SIPPs established during the arrival year, Form 8621 PFIC analysis on UK fund holdings, Form 8938 FATCA filing, FBAR via FinCEN BSA E-Filing, integrated UK Self Assessment with US Form 1040 coordination, and going-forward integrated US-UK annual workflow establishment. You can read our broader guidance on our US-UK cross-border tax advisory service.

Standard integrated US-UK split-year tax treatment. US expat UK engagement fees vary by complexity. Arrival or departure year evaluation and integrated planning typically costs £4,500 to £18,500, depending on substantive scope (asset complexity, multi-jurisdictional positioning, UK FIG regime claim integration, integrated US-UK transitional planning). Going forward, annual integrated workflow fees range from £2,800 to £12,500+, depending on complexity. Get in touch with our team today at or visit https://www.us-uktax.com/ to discuss your situation.

Conclusion

Three takeaways matter most for US expats evaluating split-year tax treatment, and the US expat UK positioning in 2026. First, the UK split-year framework under HMRC RDR3 operates through eight specific cases (Cases 1-3 for departure scenarios, Cases 4-8 for arrival scenarios) under FA 2013 Schedule 45 Part 3 — optimal case selection materially affects the substantive UK-resident portion of the arrival or departure UK tax year and the integrated UK tax outcome, with Case 5 (starting full-time work in UK) typically the principal applicable case for US expats arriving on UK employment-based relocation. Second, the integrated US-UK arrival or departure year planning incorporates the UK split-year framework alongside the US-side Form 1040 positioning (typically standard US worldwide taxation for US citizens rather than dual-status year filing which applies primarily to Green Card status changes and substantial presence test crossings), Form 1116 Foreign Tax Credit positioning across the UK-resident and UK non-resident portions intersecting with the US calendar tax year, and the post-April 2025 UK Foreign Income and Gains regime claim for qualifying arrivers producing 4-year UK tax exemption on foreign income and foreign gains. Third, the substantive split-year tax treatment US expat UK evaluation requires specialist depth on both the UK RDR3 framework and the US-side Form 1040 framework simultaneously — UK-only specialists typically lack the US-side framework integration, including Form 1116 FTC positioning across the split-year intersection, Form 8833 treaty election under Article 18(5), Form 8621 PFIC analysis, and integrated US-UK arrival year coordination, while US-only specialists typically lack the substantive UK RDR3 case selection expertise and integrated UK FIG regime coordination. Speak to a US-UK Tax adviser today — contact us at or visit https://www.us-uktax.com/.

Frequently Asked Questions About Split-Year Tax Treatment: US Expat, UK

Q: What is UK split-year treatment, and when does it apply?

A: UK split-year treatment under HMRC RDR3 guidance operates through eight specific cases under FA 2013 Schedule 45 Part 3, allowing UK tax-resident filers to split a UK tax year into separate UK-resident and UK non-resident portions for substantive UK tax purposes. The split-year framework applies to UK arrival scenarios (Cases 4-8) and UK departure scenarios (Cases 1-3) where the specific conditions for the applicable case are satisfied. For US expats arriving in or leaving the UK partway through a UK tax year (which runs from 6 April to 5 April), the split-year framework typically applies, resulting in UK-resident treatment only for the post-arrival or pre-departure portion of the UK tax year, rather than the entire UK tax year. The HMRC RDR3 reference sits at https://www.gov.uk/government/publications/rdr3-statutory-residence-test-srt.

Q: Which RDR3 case applies to me as a US expat arriving in the UK for work?

A: For US expats arriving on a UK employment-based relocation, Case 5 (starting full-time work in the UK) is the principal applicable case in most circumstances. Case 5 produces a split-year application from the date the filer starts UK full-time work satisfying the UK full-time work conditions (working more than 35 hours per week on average in the UK for at least 365 days starting in the UK tax year, no significant break). Case 8 (starting to have a UK home) is an alternative case where a UK home is established before UK employment commences. Case 4 (starting to have only a UK home) requires no overseas home retention, which is materially limiting for US expatriates who typically retain US-domiciled property. Specialist evaluation determines the optimal case selection.

Q: Do US citizens file a dual-status year US tax return when arriving in or leaving the UK?

A: Typically, no for US citizens. US citizens remain US tax residents on a worldwide income basis under IRC Section 1, regardless of their UK residence pattern — the standard Form 1040 filing applies to the full US calendar tax year. The dual-status year framework under IRC Section 7701(b)(2)(C) and Treas Reg 1.871-13 applies primarily to Green Card status changes (Green Card abandonment or first-time Green Card acquisition during the year) and to substantial presence test threshold crossings, rather than to UK arrival or departure by US citizens. Green Card holders and substantial presence test US residents may face dual-status year filing in specific UK arrival or departure scenarios. The IRS dual-status reference sits at https://www.irs.gov/individuals/international-taxpayers/dual-status-aliens.

Q: How does Form 1116 Foreign Tax Credit work in a UK split-year?

A: Form 1116 Foreign Tax Credit operates on UK Income Tax paid by the US filer, flowing through credit relief against US tax on the same income on the US Form 1040. For US citizens in a UK split-year, the substantive Form 1116 FTC analysis applies to UK Income Tax paid during the UK-resident portion of the UK tax year that overlaps with the US calendar tax year — typically UK-employment income from the UK split-year start date through the US calendar year end (December 31). The UK Income Tax substantially exceeds US tax on UK salary at typical UK higher rates, producing a substantial Form 1116 FTC carryforward under IRC Section 904(c) for future use. Specialist coordination ensures optimal Form 1116 FTC positioning across the split-year intersection.

Q: Does the UK FIG regime apply to my UK arrival year as a US expat?

A: The post-April 2025 UK Foreign Income and Gains regime under Finance Act 2025 applies to qualifying UK arrivals — UK residents in the current tax year with at least 10 consecutive prior UK non-residence tax years immediately preceding the UK arrival tax year. For US expats arriving in the UK with continuous prior US residence for at least 10 years (or other 10-year prior non-UK-residence patterns), the UK FIG regime typically applies. The 4-year UK FIG regime exemption window begins from the UK arrival tax year — Year 1 covers the UK arrival tax year (typically a split-year for mid-year UK arrivers under the applicable RDR3 case), Years 2-4 cover the subsequent three full UK tax years. The integrated split-year plus UK FIG regime positioning materially affects the substantive UK tax outcome for the arrival year and the subsequent 3 UK tax years.

Q: What happens if I don't claim split-year treatment in my UK arrival year?

A: Without a split-year treatment claim, the UK arrival year is treated as a full UK tax-resident year, producing UK tax on worldwide income (or UK-source income only where the UK FIG regime is claimed) for the entire UK tax year — including the pre-arrival portion before UK residence actually commenced. The pre-arrival portion typically includes US-source income earned by the US expat in the US before the UK relocation — without split-year treatment, which would make pre-arrival US-source income subject to UK Income Tax (or UK-exempt under the UK FIG regime, where applicable), producing a materially adverse UK tax outcome for the arrival year. A proper split-year claim under the applicable RDR3 case is materially important for UK arrival-year positioning.

Q: When do I claim UK split-year treatment on my UK Self Assessment?

A: UK split-year treatment is claimed on the UK Self Assessment return for the relevant UK tax year (the arrival or departure UK tax year). The standard UK Self Assessment deadline of 31 January following the end of the UK tax year applies — for example, for the 2025-26 UK tax year (ending 5 April 2026), the UK Self Assessment with a split-year claim is filed by 31 January 2027, with supporting documentation establishing the applicable RDR3 case selection. The UK Self Assessment form includes specific boxes for a split-year claim under the applicable case. Specialist UK Self Assessment preparation, including substantive split-year case selection documentation, is materially important to the substantive UK tax outcome.

Q: Can US-UK Tax help me with my UK arrival or departure year split-year planning?

A: Yes. Our standard integrated US-UK split-year tax treatment US expat UK engagement covers comprehensive arrival or departure diagnostic, UK Statutory Residence Test analysis, UK RDR3 case selection analysis across Cases 1-8 with optimal case identification, UK split-year application documentation on UK Self Assessment, post-April 2025 UK Foreign Income and Gains regime eligibility evaluation and claim coordination for qualifying arrivers, US-side Form 1040 positioning (standard US worldwide taxation for US citizens or dual-status year filing where applicable for Green Card holders and substantial presence test residents), integrated Form 1116 Foreign Tax Credit positioning across UK-resident and UK non-resident portions intersecting with the US calendar tax year, Form 8833 treaty election under Article 18(5) on UK workplace pensions and SIPPs, Form 8621 PFIC analysis on UK fund holdings, Form 8938 FATCA filing, FBAR via FinCEN BSA E-Filing, integrated UK Self Assessment with US Form 1040 coordination, and going-forward integrated US-UK annual workflow establishment. Arrival or departure year evaluation and integrated planning fees typically range from £4,500 to £18,500, depending on complexity, with going-forward annual integrated workflow fees ranging from £2,800 to £12,500+. Contact to discuss your situation.