Estate and Investment Planning When Returning to the US: The Pre-Return Checklist

Estate and investment planning when returning to the US works best in the months before you fly, not after you land. Because the US already taxes citizens on worldwide income, your sharpest levers are on the UK side: realizing gains at UK rates, unwinding PFIC-laden ISAs and funds, and timing disposals around the temporary non-residence rule. Get the sequence right before departure.

By the TaxYork Cross-Border Tax Team — reviewed by a US-UK dual-qualified adviser (CPA / Enrolled Agent).

Why does timing matter so much before you return to the US?

Timing matters because the two tax systems overlap for a window, and that overlap is where the planning lives. The IRS already taxes a US citizen in the UK on worldwide income and gains. What changes on return is your UK exposure — you lose UK allowances, UK reliefs and, crucially, the shelter of being outside the UK's anti-avoidance net. The pre-return period is the one moment when you can use UK rules to your advantage while the US net is at its loosest.

The core principle: the US side is largely fixed, the UK side is flexible

For a US person, the US tax treatment of most income and gains is broadly settled — citizenship-based taxation follows you wherever you live. The variables you can still move are the UK ones: when you dispose of an asset, whether you crystallize a gain inside a UK tax year, and whether you carry a punitive PFIC into your US-resident years. A disposal made three weeks before you become a UK non-resident can land in a completely different place from the same disposal made three weeks after.

Build the checklist around your departure date.

Fix your likely UK departure date first, then work backward. The UK's Statutory Residence Test decides when your UK residence ends, and a split-year treatment often applies in the year of departure. Every action below — harvesting gains, closing PFIC wrappers, funding US-compliant accounts — is dated relative to that departure point.

What should be on the pre-return investment checklist?

The short answer: unwind anything the IRS treats as a PFIC, decide which gains to realize while still UK-resident, and set up clean US-compliant accounts before you land. Each item has a UK tax cost and a US tax cost, and the goal is to pay the smaller one deliberately rather than the larger one by accident.

Unwind PFICs: ISAs, OEICs, investment bonds.

Most pooled UK investments — OEICs, unit trusts, investment trusts and the funds held inside a Stocks and Shares ISA — are Passive Foreign Investment Companies in the US's eyes. A UK ISA is tax-free to HMRC, but the IRS grants it no shelter at all: the wrapper does not change the fund's PFIC status. Holding a PFIC forces annual Form 8621 reporting (see the IRS overview About Form 8621) and, absent a mark-to-market or QEF election, the punitive Section 1291 excess-distribution regime with interest charges. Selling these holdings before or around your return removes an expensive, paperwork-heavy problem from your US-resident years.

UK offshore reporting-fund and non-reporting-fund status is a separate UK question — check it before you sell, because a non-reporting fund can turn a UK capital gain into UK income.

Decide which gains to realize while UK-resident.

The UK annual exempt amount is just £3,000 for 2025/26, down from £12,300 in 2022/23, so the allowance itself is now modest. UK CGT on shares runs at 18% within your remaining basic-rate band and 24% above it for 2025/26, as set out in the HMRC guidance on Capital Gains Tax and its rates and allowances. Compare that with your prospective US federal long-term capital gains rate and your state rate once home. Where the UK rate is lower, realizing gains before departure — and resetting your cost basis to a higher amount — can reduce the eventual US bill. This is asset-by-asset arithmetic, not a blanket rule.

Set up US-compliant accounts before you land.

Open US brokerage capacity before you return, not after. US-domiciled ETFs and mutual funds are not PFICs and sidestep Form 8621 entirely. Arriving with cash and a ready US account lets you rebuild a clean, US-compliant portfolio immediately, rather than carrying UK funds into your first US tax year and inheriting their reporting burden.How does the UK temporary non-residence rule affect a departing US person?

It can pull gains back into the UK tax net. If you have been a UK resident in at least four of the seven tax years before you left, and you return within roughly five years, the UK's temporary non-residence rule can tax gains realized during your absence in the tax year you come back. For a US person merely passing through the UK on the way home, this usually is not in play — but for anyone who lived in the UK for years, it is a real trap.

The five-year trap in practice

The rule targets people who leave, sell assets held before departure while non-resident, and return within about five years. Gains on those pre-owned assets become chargeable to UK CGT in the year of return, as explained in HMRC helpsheet HS278 Temporary non-residents and Capital Gains Tax. Assets you both acquire and dispose of entirely during the non-resident period generally fall outside the non-resident period. If you are a long-term UK resident planning a return to the US and back to the UK, model this carefully — HMRC has been writing to taxpayers about undeclared temporary-non-residence gains from 2018/19 onwards.

Where FIG changes the picture on the way in

The remittance basis ended on 6 April 2025 and was replaced by the four-year Foreign Income and Gains (FIG) regime. FIG matters mainly to people arriving in or returning to the UK after at least ten consecutive non-UK-resident years — they can claim relief on foreign income and gains for their first four UK-resident years, per the HMRC guidance on how to claim the 4-year foreign income and gains regime. For a US person moving in the opposite direction (leaving the UK for the US), FIG is chiefly relevant if a later return to the UK is on the cards. Note that claiming FIG costs you the UK personal allowance and the CGT annual exempt amount for that year. General rules on tax on foreign income continue to apply while you remain UK-resident.

What are the estate and gift tax issues when returning to the US?

A US citizen is taxed on their worldwide estate, full stop — moving back does not create that exposure; it simply removes the UK-residence overlay. The 2025 federal unified exclusion is $13.99 million per person, rising to $15 million in 2026 under the One Big Beautiful Bill Act. The IRS explains the basics of the Estate Tax. Most families sit well below that, but the planning still matters for larger estates and for anyone holding assets on both sides of the Atlantic.

Worldwide estate and the unified exclusion

The US estate and gift tax is unified: lifetime taxable gifts reduce the exclusion amount available at death, as the IRS explains in its Estate and Gift Tax FAQs. The annual gift exclusion is $19,000 per recipient for 2025 and does not touch the lifetime amount. A married US couple can combine their exclusions, resulting in $27.98 million for 2025. These are generous thresholds, but they are set against your worldwide estate, including UK property and pensions.

The US-UK estate and gift tax treaty and domicile

The US-UK estate and gift tax treaty allocates primary taxing rights largely by domicile, with the situs country given priority over real property and tangible personal property; the IRS lists the relevant estate and gift tax treaties. UK domicile for these purposes is a separate concept from income-tax residence — you can be a US resident for income tax yet still carry UK domicile consequences, or vice versa. The treaty also allows a UK-domiciled person to access the full US exclusion rather than the $60,000 floor that applies to non-domiciliaries holding US-situs assets. Domicile is fact-heavy; get it reviewed before you move.

Trusts: mind the foreign non-grantor trust throwback

If you sit inside or plan to create a trust, structure matters enormously once you are a US resident. A foreign non-grantor trust can trigger the US throwback rule, taxing accumulated distributions at compressed rates with an interest charge on the deferral. Review any UK or offshore trust arrangements before return so distributions and elections are timed sensibly rather than left to chance.

How should pensions and retirement accounts be handled?

Consolidate and simplify before you go, but tread carefully. A UK SIPP or workplace pension is generally recognized under the US-UK income tax treaty, so pension growth is not usually a live PFI issue, unlike an ISA. That treaty protection is one reason pensions are often left in place while ISAs are unwound.

SIPPs, workplace pensions, and US treatment

UK-registered pensions typically benefit from treaty provisions covering contributions and growth. However, the treatment of lump sums and the UK's 25% tax-free amount is more nuanced in the US. Do not collapse a UK pension in a panic — the tax-free UK element is not automatically tax-free to the IRS. Take advice on the specific scheme before drawing anything.

Roth conversions and the low-income window

The tax year you move can be a low-income year, which sometimes opens a window for Roth conversion planning at a lower marginal rate. This interacts with UK residence, the foreign tax credit and the timing of any UK disposals, so it belongs in a coordinated plan rather than as a standalone move.

Case study: unwinding an ISA-heavy portfolio before the move home

An anonymized example. "Rachel", a US citizen, had lived in London for eleven years and accepted a job back in Boston. Her portfolio held roughly £180,000 across two Stocks and Shares ISAs and three UK OEICs — every one of them a PFIC to the IRS, and she had never filed Form 8621. She planned to keep them "because they were doing fine".

Working eight months out from her move, we mapped each holding. The ISAs and OEICs were sold across two UK tax years while she was still UK-resident, using her annual exempt amounts and paying UK CGT at 18%/24% on the balance — a known, moderate cost. Proceeds were moved into US-domiciled ETFs in a newly opened US brokerage account. Because she had been a UK resident for well over four of the prior seven years, we also confirmed she had no plan to return to the UK within five years, keeping the temporary non-residence rule out of scope. She landed in Boston with a clean, PFIC-free portfolio and no Form 8621 backlog waiting for her first US filing season.

Speak to TaxYork before you book the flight.

Repatriation planning rewards early action and punishes delay. If you are a US person preparing to leave the UK, TaxYork's dual-qualified team can build your pre-return checklist — PFIC unwinding, CGT timing, estate and treaty positioning, and pension review — in the right order and the right tax years.

Contact us at hello@taxyork.com | 020 3488 8606 | taxyork.com to arrange a cross-border planning consultation.