US and UK Tax Advisors — Pre-Departure Planning When Leaving the US for the UK

Meta Description: US and UK Tax Advisors on pre-departure planning: final US return, 401k decisions, state ties, US property sale, business structures. Call 0333–8807974.

Tags: Pre-Departure Planning, Leaving the US, Moving to UK, 401k, IRA, State Residency, US Property Sale, Social Security, Final Year Return, 2026

Introduction

The most expensive tax mistakes for Americans moving to the UK are made before the flight — on the US side of the departure, not after arrival.

Specialist **US and UK Tax Advisors** who plan pre-departure understand that the final year of US residency is a unique planning window. The 401(k) rollover decision, the US real estate sale, the S corporation winding-up, and the state residency severance all carry consequences that cannot be corrected after departure. Each action completed before leaving the United States is governed only by US rules. Each action deferred until after UK arrival is governed by both systems simultaneously — and the combined tax cost is almost always higher.

This guide focuses exclusively on the US-side pre-departure actions for an American moving to the UK. It covers the final year US return structure, 401(k) and IRA decisions, the US property sale before departure, closing or restructuring US business entities, state residency severance, and the Social Security considerations that most pre-departure guides ignore. Contact Jungle Tax at https://www.jungletax.co.uk/ before you leave.

What Are US and UK Tax Advisors in the Pre-Departure Context?

The US-Side Departure Specialist

US and UK Tax Advisors who specialise in pre-departure planning understand the US tax system from the inside — as practitioners who know the IRS rules on departure-year returns, the state residency severance requirements for California and New York, the 401(k) and IRA rules for departing residents, and the treatment of US business entities when the owner moves abroad. They also understand how every US-side decision affects the UK tax position after arrival — because many US actions taken before departure have UK consequences in the first UK tax year.

A US-only adviser without UK knowledge cannot advise on the UK consequences of a 401(k) rollover completed the week before arrival. A UK-only adviser without US knowledge cannot advise on the final year US return or the state residency severance requirements. The **US and UK Tax Advisors** at Jungle Tax understand both — and plan the US-side departure alongside the UK-side arrival.

Who This Guide Is For

This guide covers US citizens and permanent residents who plan to move to the UK — from any US state — and want to understand all US-side tax actions to complete before departure. It covers both employees moving for work and individuals moving for personal reasons.

The IRS guidance on US citizens moving abroad is published at:

https://www.irs.gov/individuals/international-taxpayers/us-citizens-and-resident-aliens-abroad

The Departure Year Is a Partial Year — With Specific Filing Consequences

The year of departure is a partial-year US residency year. From 1 January through the date of departure, the individual is a US resident for tax purposes and is subject to US tax on worldwide income. From the departure date to 31 December, the individual is a non-resident — subject to US tax only on US-source income. The US federal return for the departure year covers both periods on a single Form 1040, with a note indicating the dates of US residency.

The departure year return is more complex than a standard annual return. The adviser must split income between the resident and non-resident periods, apply the FEIE or FTC to the non-resident period where applicable, and ensure that any US-source income arising after departure is correctly reported as non-resident income.

Why Pre-Departure Planning With US and UK Tax Advisors Matters in 2026

The 401(k) Rollover Decision Has Permanent Consequences

A 401(k) account left with a former US employer after departure is subject to required minimum distributions from age 73 — regardless of where the account holder lives. The RMD is taxable in the United States as ordinary income. For a US citizen living in the UK, the RMD may also be taxable in the UK, depending on the Article 17 treaty election position for employer-sponsored plans. Rolling the 401(k) into an IRA before departure simplifies post-departure administration and provides more flexibility in the withdrawal timeline.

The rollover itself is tax-free — it is not a taxable distribution. But the timing matters. A rollover completed while the individual is a California resident may trigger California state income tax on the rollover amount if the rollover is treated as a taxable distribution in California. The adviser confirms the state tax treatment of the rollover before it is executed.

S Corporation and LLC Structures Must Be Addressed Before Departure

A US S corporation owned by a non-resident alien — which the individual becomes on departure — loses its S corporation election automatically. An S corporation that loses its election converts to a C corporation. The conversion can have significant tax consequences — including the built-in gains tax on appreciated assets held at the time of conversion. A US citizen who owns an S corporation and plans to move to the UK must either sell the S corporation, convert it to an LLC, or transfer it to a qualifying trust before departure.

Our guide to pre-immigration planning before moving to the UK covers the UK arrival side of these decisions — including the PFIC restructuring and Roth conversion timing.

US Real Estate Sales Before Departure Avoid FIRPTA Withholding

A US citizen who sells US real estate after establishing UK residency is still subject to US tax on the gain — but the transaction is not subject to FIRPTA withholding, because FIRPTA applies to non-US persons. A US citizen remains a US person regardless of UK residency. However, the UK also taxes the gain as a UK resident, because UK residents pay UK CGT on worldwide gains. Selling US real estate before departure — while still a US resident — avoids UK CGT on the gain entirely. The sale is taxed only in the United States.

The Key US-Side Pre-Departure Planning Actions

The Final Partial-Year US Return — Structuring the Departure Year

The departure-year US return covers two periods: the US resident period (1 January to the departure date) and the non-resident period (from the departure date to 31 December). The adviser structures the return to minimize the combined tax across both periods. Income earned in the US resident period is taxed as resident income — subject to the standard deductions, exemptions, and credits available to a resident. Income earned during the non-resident period is taxed under the non-resident rules, which may limit the deductions available.

The adviser also reviews whether any year-end planning actions — Roth conversions, charitable deductions, capital loss harvesting — should be completed in the resident period before departure, rather than deferred to the UK arrival year. Actions completed in the US resident period of the departure year are governed only by US rules — no UK interaction arises.

401(k) and IRA Decisions Before Departure

A 401(k) left with a former employer after departure remains subject to plan rules — including investment restrictions, withdrawal fees, and RMD requirements. Rolling the 401(k) to an IRA before departure provides full investment flexibility, consolidates retirement assets, and simplifies post-departure administration. The rollover is direct — from the 401(k) plan trustee to the IRA custodian — and is not a taxable distribution.

For a traditional IRA, the US and UK Tax Advisors at Jungle Tax review whether a pre-departure Roth conversion is appropriate. A Roth conversion completed in the US resident period of the departure year is taxable only in the United States — no UK income tax arises, because the individual is not yet a UK resident. A Roth conversion completed after UK residency begins may also attract UK income tax. The adviser calculates the optimal conversion amount — the amount that can be converted at the US marginal rate without triggering excess tax — before the departure date.

Selling US Real Estate Before Departure

The sale of a US principal residence before departure is exempt from US federal capital gains tax on the first $250,000 of gain ($500,000 for married filing jointly) under Section 121 — provided the principal residence test is met. No UK CGT arises — because the individual is not yet a UK resident at the time of sale. After departure, the sale of a US property triggers UK CGT on the gain at 20 percent — in addition to any residual US tax. The tax savings from selling before departure can be significant for a property that has appreciated substantially.

For US investment properties — rental properties, buy-to-let properties, or vacation homes — the adviser models the capital gain and any applicable depreciation recapture before the sale. Depreciation recapture on US rental property is taxed at 25 percent in the United States — and is separate from the standard long-term capital gains rate. The adviser confirms the optimal timing of the sale — before or after departure — based on the specific tax cost in each scenario.

S Corporation and Partnership Restructuring

A US S corporation automatically loses its S election when a non-resident alien becomes a shareholder. A US citizen who moves to the UK does not become a non-resident alien — they remain a US citizen and can continue to hold S corporation shares. However, many S corporation operating agreements restrict ownership to US residents, and the practical administration of a US S corporation from the UK can be complex.

The **US and UK Tax Advisors** at Jungle Tax review every US business structure before departure. An S corporation held by a US citizen who moves to the UK can typically continue — but the adviser reviews whether the S election conditions are met, whether any state-level S election must be separately addressed, and whether the UK has any tax charge on the S corporation income in the hands of a UK resident shareholder.

How a Specialist Plans the US-Side Departure

Stage One — Full US Asset and Income Inventory

The adviser begins by inventorying all US-based assets, income sources, and business structures. This includes: US real estate (principal residence and investment properties), US retirement accounts (401(k), IRA, Roth IRA), US brokerage accounts, US business interests (S corporations, LLCs, partnerships), US bank accounts, US health savings accounts, and any outstanding US tax obligations or installment agreements.

The adviser also identifies every US state connection — the state of domicile, states where the individual owns property or operates a business, and states where the individual earns income. Each state connection must be addressed before departure — some states assert residency long after physical departure unless the connections are formally severed.

Stage Two — State Residency Severance

California and New York are the two states most aggressive in asserting continued residency after departure. California’s Franchise Tax Board requires evidence that the taxpayer has established a new domicile, not just moved temporarily. New York State and New York City impose residency taxes on individuals who maintain a permanent place of abode in the state — even after physical departure.

The adviser prepares a severance plan for each state connection. For California: selling or renting the primary residence to an unrelated party, closing California bank accounts, changing voter registration, obtaining a new driving license in a different state or the UK, and resigning from California-based clubs and professional organizations. For New York, the same steps, plus confirming that no permanent place of abode is maintained in New York State. The adviser documents every step and advises on the departure date to minimize the risk of the state asserting continued residency.

Stage Three — Retirement Account Optimization

The adviser reviews every retirement account and confirms the optimal pre-departure action for each. The 401(k) rollover to an IRA is typically recommended to simplify administration and maximize flexibility. The Roth conversion amount is calculated to confirm the maximum amount that can be converted during the US resident period of the departure year at the applicable marginal rate, without triggering excess tax. The adviser also reviews the health savings account — HSA balances cannot be contributed to after departure, but existing balances can be retained and used for qualifying medical expenses.

Stage Four — US Real Estate and Business Decisions

The adviser models the tax cost of selling each US property before versus after departure. For properties where the pre-departure sale is significantly more tax-efficient — particularly where the Section 121 exclusion applies to the principal residence — the adviser recommends completing the sale before the departure date. For properties where the tax difference is modest, the adviser weighs the administrative cost of managing US real estate from the UK against the tax saving from a pre-departure sale.

For US business structures, the adviser confirms the tax treatment under each scenario — continued operation from the UK, conversion to a different structure, or sale before departure. The adviser prepares the departure year return for any business structures that are closed or sold before departure.

The IRS guidance on departing aliens and their tax return obligations is published at:

https://www.irs.gov/individuals/international-taxpayers/departing-alien-clearance-sailing-or-departure-permit

Stage Five — Final US Return Filing and Ongoing Compliance

The adviser prepares the US federal return for the departure year, covering both the resident and non-resident periods. The return identifies the departure date, splits income between the two periods, and applies the applicable credits and deductions for each period. Where the individual has Social Security contributions — either from employment or self-employment — the adviser confirms the Totalisation Agreement treatment for the first years of UK employment.

The adviser also establishes the post-departure annual US filing program — because the individual remains a US citizen and continues to file US federal returns annually. The annual program covers the post-departure worldwide income reporting, FBAR, Form 8938, and any ongoing US business or real estate reporting obligations.

Case Study — Pre-Departure Planning for a New York Executive

The Client’s Position

Marcus is a US citizen living in Manhattan. He is relocating to London for a senior role at a UK financial services firm, starting in October 2026. He contacted Jungle Tax in March 2026 — seven months before his planned departure.

His US financial position: a Manhattan apartment worth $2.4 million (purchase price $1.1 million, mortgage $600,000), a 401(k) with his current employer worth $380,000, a traditional IRA worth $140,000, a US brokerage account holding US equities and three US-domiciled ETFs, and a 25 percent interest in a New York LLC operating as a management consultancy.

The Pre-Departure Planning Actions

Jungle Tax identified and completed the following US-side pre-departure actions before Marcus’s October 2026 departure.

The Manhattan apartment was sold in August 2026 — two months before departure. The capital gain was $700,000 ($2,400,000 proceeds minus $1,100,000 purchase price minus $600,000 mortgage repayment, on a cash basis). The Section 121 exclusion for a single filer covers $250,000 of the gain. The taxable gain was $450,000 — taxable in the United States at the long-term capital gains rate. No UK CGT arose — Marcus was not yet a UK resident. After the departure, the same sale would have triggered UK CGT of approximately £72,000 (20 percent of the sterling equivalent of $450,000 in addition to the US federal tax.

The 401(k) was rolled to an IRA before departure — a direct rollover from the employer plan trustee to a Fidelity IRA. No tax arose on the rollover. The adviser calculated that Marcus could convert $45,000 of the traditional IRA to a Roth IRA in the US resident period of the departure year — at the 22 percent marginal rate — without triggering the net investment income tax. The Roth conversion was completed in September 2026.

The New York LLC was reviewed. Marcus’s 25 percent interest does not automatically cause the LLC to lose its pass-through status — as a US citizen, Marcus can continue to hold LLC interests from the UK. The adviser confirmed the UK treatment of LLC income for a UK resident shareholder and included LLC reporting in the UK annual compliance program.

New York City and State residency were formally severed before departure. Marcus sold the Manhattan apartment, eliminating the permanent place of abode. He updated his voter registration to reflect a move to a new state. His New York driving license was canceled and replaced with a UK driving license before departure.

The Outcome

The pre-departure sale of the Manhattan apartment saved Marcus approximately £72,000 in UK CGT. The Roth conversion of $45,000 was completed at a 22 percent US marginal tax rate — approximately $9,900 in US tax — with no UK income tax. The 401(k) rollover consolidated Marcus’s retirement assets and simplified post-departure administration. New York residency was formally severed — eliminating the ongoing New York City income tax obligation on UK employment income.

Contact our **US and UK Tax Advisors** team at hello@jungletax.co.uk or 0333–8807974 if you are planning a move to the UK from the United States.

Common Mistakes in US-Side Pre-Departure Planning

Selling the US Home After UK Arrival — Not Before

The sale of a US principal residence before departure attracts only US federal capital gains tax, with the Section 121 exclusion available on the first $250,000 of gain. Upon arrival in the UK, the same sale attracts UK CGT at 20 percent on the full gain. For a home with $500,000 of appreciation above the Section 121 ceiling, the UK CGT on the excess gain after arrival is approximately £80,000 — a cost that a pre-departure sale eliminates. Many Americans defer the home sale until after arrival for logistical reasons — not realizing the tax cost of that decision.

Leaving the 401(k) With the Former Employer After Departure

A 401(k) left with a former employer is subject to that plan’s investment options, withdrawal fees, and RMD rules. Managing a US employer plan from the UK — across time zones, with different customer service standards — is significantly more complex than managing a self-directed IRA. Rolling the 401(k) to an IRA before departure takes one administrative step. The rollover is tax-free. The cost of not rolling — n time complexity and restricted investment options — is an ongoing inconvenience that compounds over the years.

Not Formally Severing New York or California Residency

New York City imposes income tax at up to 3.876 percent on New York City residents, including on UK employment income, if the individual is considered a New York City resident. A taxpayer who maintains a Manhattan apartment after moving to the UK — even if they visit only occasionally — may be treated as a New York City resident for tax purposes, because they maintain a permanent place of abode in the city. Selling the New York property before departure and formally severing residency eliminates this exposure. Keeping the property and assuming New York will not assert residency is a risk that many Americans underestimate.

Not Addressing the S Corporation Before Departure

A US S corporation whose shareholder moves to the UK does not automatically lose its S election — because the shareholder remains a US citizen, not a non-resident alien. However, many states impose separate S election requirements, and some state elections may be affected by the shareholder’s change of domicile. The adviser reviews every state-level S election before departure and confirms that the corporation’s structure is compliant with both federal and state S corporation rules after the owner’s move.

The IRS guidance on S corporations is published at:

https://www.irs.gov/businesses/small-businesses-self-employed/s-corporations

Not Completing the Roth Conversion Before Departure

A Roth conversion completed in the US resident period of the departure year is taxable only in the United States. After UK residency begins, the same conversion may also attract UK income tax, because the UK does not automatically recognize the tax-deferred status of US retirement accounts in the same way that the Article 17 election covers SIPPs. The pre-departure window is the most efficient time to convert, with no UK interaction. Many Americans defer the decision to convert until after arrival and pay a higher combined tax as a result.

How Jungle Tax Can Help

Jungle Tax is a specialist US-UK cross-border tax advisory firm whose team includes IRS Enrolled Agents and UK-qualified tax practitioners who serve as **US and UK Tax Advisors for Americans planning to relocate from the United States to the UK. We conduct a full US-side pre-departure assessment — inventorying every asset, retirement account, business structure, and state residency connection — before recommending a departure plan. We model the tax cost of every major decision on both sides of the border: US property sale timing before versus after departure; 401(k) rollover and Roth conversion timing; S corporation treatment under UK residency; and state residency severance requirements for California and New York. We prepare the departure year US federal return — covering both the resident and non-resident periods — and establish the post-departure annual US filing program. We coordinate the US-side departure plan with the UK-side arrival plan, ensuring that every action taken before departure is accurately reflected in the first UK self-assessment return. You can find further information on our page at https://www.jungletax.co.uk/, or read our guide to pre-immigration planning before moving to the UK — the UK arrival side. Contact our team at [hello@jungletax.co.uk or call 0333–8807974](https://www.jungletax.co.uk/#contact)** today.

Conclusion

The US-side pre-departure planning window closes on the day of departure. Every action taken before leaving the United States is governed solely by US law. Every action deferred until after UK arrival is governed by both systems simultaneously — and the combined cost is almost always higher. Specialist US and UK Tax Advisors plan the US side of the departure before the flight is booked.

Three points matter most. First, sell the US principal residence before departure — the Section 121 exclusion applies, and no UK CGT arises. After departure, the same sale triggers UK CGT at 20 percent on the full gain above the exclusion ceiling. Second, complete the 401(k) rollover and Roth conversion before departure — both are governed only by US rules if completed before UK residency begins. Third, formally sever California or New York residency before departure — not after. The FTB and New York State both aggressively assert residency, and the tax cost of maintaining state residency on UK employment income is high.

Speak to a Jungle Tax adviser today — contact us at **hello@jungletax.co.uk** or visit our website ahttps://www.jungletax.co.uk/ to begin your pre-departure planning.

Frequently Asked Questions About Pre-Departure Planning When Leaving the US for the UK

Q: Do I need to file a US tax return in the year I leave the United States?

Yes. The year of departure is a partial-year US residency year. You file a standard Form 1040 covering both the period of US residency (1 January to your departure date) and the non-resident period (departure date to 31 December). The return identifies your departure date. Income earned during the US resident period is reported as resident income. US-source income arising during the non-resident period — such as rental income from a US property or dividends from a US brokerage account — is reported as non-resident income on the same return. A specialist US and UK tax adviser prepares the departure-year return to split income between the two periods correctly.

Q: Should I sell my US home before or after moving to the UK?

Selling your US principal residence before departure is almost always the more tax-efficient option, as the Section 121 exclusion applies — exempting the first $250,000 of gain (or $500,000 for married filing jointly) from US federal capital gains tax. No UK CGT arises because you are not yet a UK resident. After arrival in the UK, the same sale is exempt from UK CGT on the pre-arrival gain (under the UK basis step-up rules), but the post-arrival gain attracts UK CGT at 20 percent. For properties that have appreciated significantly above the Section 121 ceiling, the UK CGT saving from a pre-departure sale can be substantial.

Q: Can I roll my 401(k) to an IRA before moving to the UK?

Yes — and it is generally recommended. A 401(k) rolled to an IRA before departure consolidates your retirement assets, provides full investment flexibility, and simplifies post-departure administration. The rollover is direct — from the 401(k) plan trustee to the IRA custodian — and is not a taxable distribution. State tax implications should be confirmed before the rollover is executed — some states may tax rollovers differently than standard distributions. Once the IRA is established, you can consider a pre-departure Roth conversion of a portion of the IRA balance — at a time when only US federal tax applies to the converted amount.

Q: What happens to my US S corporation when I move to the UK?

A US citizen who moves to the UK remains a US citizen — not a non-resident alien. An S corporation can have non-resident US citizen shareholders without automatically losing its S election. However, the practical and tax implications of operating a US S corporation from the UK are complex. S corporation income passes through to the shareholder and is reported on the US federal return. As a UK resident, that same income may also be taxable in the UK — depending on the nature of the business and the UK-US tax treaty treatment. A specialist US and UK tax adviser reviews the S corporation structure before departure and advises on whether to continue, convert, or sell the entity.

Q: How do I sever California residency before moving to the UK?

California’s Franchise Tax Board requires evidence that you have established a new domicile — not simply left California temporarily. To sever California residency: sell or rent your California home to an unrelated third party; close California bank accounts; change your voter registration to a different state; obtain a driving license from a different state or the UK; resign from California clubs, professional organizations, and boards; and document your intention to establish a permanent home outside California. The FTB can assert continued residency for years after physical departure if the connections remain. A specialist adviser prepares a documented severance plan and advises on the timing of departure to minimize the FTB’s basis for continued residency.

Q: What happens to my Social Security contributions when I move to the UK?

Your prior US Social Security contributions are not lost when you move to the UK. You remain entitled to US Social Security benefits based on your US earnings history — regardless of where you live. If you work in the UK and pay UK National Insurance contributions, the US-UK Totalization Agreement prevents double Social Security contributions on the same earnings — you pay into one system, not both. Once you reach Social Security benefit age, you can receive US Social Security payments in the UK. The payments are generally subject to US federal income tax (up to 85 percent of the benefit may be taxable). They may also be taxable in the UK, depending on the treaty’s treatment. A specialist adviser confirms the Totalization Agreement position for your specific employment situation.