US 401(k), IRA and UK Pension Planning for UK-US Movers
For individuals who have lived and worked in both the United Kingdom and the United States, retirement planning involves navigating two of the world's most complex pension tax systems — and a bilateral tax treaty that, while detailed, leaves several important issues unresolved. This guide sets out how US 401(k) plans, Individual Retirement Accounts (IRAs), and UK pensions interact, what the transfer rules do and do not permit, and the key planning considerations for those managing assets in both systems.
The UK-US Double Taxation Agreement: Article 17
The United Kingdom and United States have a Double Taxation Agreement (DTA) that has been in force since 2003. Article 17 covers pensions and governs how pension income is taxed for cross-border individuals.
The general rule under Article 17 is that pension income is taxable only in the country of residence at the time of payment. A UK resident receiving US Social Security or a 401(k) distribution should pay UK tax on that income, not US tax. A US resident receiving a UK pension should pay US tax.
However, Article 17 contains a critical exception for US persons. The United States taxes its citizens and green card holders on worldwide income regardless of residence — a principle unique among developed economies. The DTA's saving clause (Article 1(4)) preserves the US's right to tax its own citizens as if the treaty did not exist. This means that US citizens living in the UK, or UK citizens living in the US who hold green cards, may face taxation in both countries on pension income, relying on foreign tax credit mechanisms to prevent double taxation rather than the treaty exemption.
Government service pensions (paid by the state) are generally taxable only in the state that pays them — so UK Civil Service pension recipients living in the US pay UK tax on that pension, not US tax.
401(k) Plans: What They Are and Why They Are Not QROPS
A 401(k) is a US employer-sponsored defined contribution retirement plan, roughly analogous to a UK workplace pension. Contributions are made pre-tax (traditional 401(k)) or after-tax (Roth 401(k)), and the fund grows within a tax-advantaged wrapper.
Traditional 401(k) contributions reduce US taxable income in the year they are made. Withdrawals in retirement are taxed as ordinary income. Roth 401(k) contributions are made from post-tax income, with qualifying withdrawals tax-free.
A 401(k) is not a QROPS (Qualifying Recognised Overseas Pension Scheme). This means:
- You cannot transfer a UK registered pension scheme to a 401(k). Any such transfer would constitute an unauthorised payment from the UK scheme and would trigger HMRC charges of up to 55% of the value transferred.
- You cannot transfer a 401(k) into a UK SIPP or personal pension as a pension-to-pension transfer.
The two systems are entirely separate. Assets built up in each must be managed and eventually drawn within their respective frameworks.
401(k) access rules
The standard minimum distribution age for a 401(k) is 59½. Withdrawals before that age are subject to a 10% early withdrawal penalty (in addition to income tax), with limited exceptions (separation from service at age 55, certain hardship withdrawals, substantially equal periodic payments under IRS Rule 72(t)).
Required Minimum Distributions (RMDs) must begin by April 1 following the year you reach age 73 (under current SECURE 2.0 Act rules).
IRA Planning for UK-US Movers
Individual Retirement Accounts come in two main forms — traditional IRA and Roth IRA.
Traditional IRA: Contributions may be tax-deductible (depending on income and whether you have access to a workplace plan). Growth is tax-deferred. Withdrawals are taxed as ordinary income. The contribution limit for 2026 is US$7,500 (US$8,600 for those aged 50 and over).
Roth IRA: Contributions are made post-tax. Qualified withdrawals — after age 59½ and after the account has been open for five years — are tax-free in the United States.
Roth IRA treatment in the UK
The Roth IRA raises a significant planning issue for individuals who are UK resident. HMRC has historically not recognised the Roth IRA's US tax-free status for UK tax purposes. From HMRC's perspective, a Roth IRA is a foreign pension arrangement, and the tax-free treatment granted under US law does not automatically carry over into UK tax treatment.
The practical consequence is that a UK resident holding a Roth IRA may find that:
- Contributions to the Roth IRA (made from US post-tax earnings while UK resident) do not attract UK tax relief.
- Investment growth within the Roth IRA may be taxable in the UK in the year it arises, depending on how HMRC categorises the arrangement and how the UK individual's US income is classified.
- Distributions from the Roth IRA that are tax-free in the US may be partially or fully taxable in the UK as pension income.
The position has not been authoritatively settled by UK case law or binding HMRC guidance specific to Roth IRAs, and different advisers take different positions. If you hold a Roth IRA and are UK resident, bespoke advice from a US-UK dual-qualified tax adviser is essential.
IRAs are also not QROPS and cannot receive transfers from UK pension schemes.
UK Pension Access: Age 57 from 2028
The UK minimum pension age is currently 55 and will rise to 57 on 6 April 2028. US 401(k) plans allow penalty-free withdrawals from 59½. This creates a 2.5-year window (between 57 and 59½) during which a UK-US mover could access their UK pension but would face a US penalty on 401(k) withdrawals. Conversely, between 55 and 57 (or after the age 57 change) there is a short window where the 401(k) allows access (at 59½) before the UK pension minimum age.
The asymmetry in access ages is relevant for liquidity planning — those approaching retirement need to model which pot is accessible when, and at what tax cost.
FBAR Reporting of UK Pensions
US persons (citizens, green card holders, and certain resident aliens) are subject to the Foreign Bank Account Report (FBAR) filing requirement under the Bank Secrecy Act. An FBAR must be filed if the aggregate value of foreign financial accounts exceeds US$10,000 at any point during the calendar year.
The FBAR question for UK pensions is unsettled but significant. The IRS's guidance (FinCEN) has stated that FBAR applies to foreign financial accounts, and there is an argument that a UK pension pot held in an individual SIPP or personal pension is a foreign financial account for these purposes. The IRS has pursued individuals for failing to report foreign pension accounts on FBAR.
However, the IRS has also indicated that certain pension-type arrangements with no individual account balance (such as defined benefit schemes where you have a right to a future income but no identifiable pot) may not require FBAR reporting in all cases.
In addition to FBAR, US persons may need to report UK pension assets under FATCA (Foreign Account Tax Compliance Act) using Form 8938, and the Foreign Trust rules under IRS Form 3520/3520-A may be triggered in some cases, particularly for self-invested arrangements.
The penalties for FBAR non-compliance are severe — up to US$10,000 per non-wilful violation and up to the greater of US$100,000 or 50% of the account value for wilful violations. This is an area where compliance advice from a US-qualified tax professional is not optional.
Managing Accumulation in Both Systems
For UK-US movers who are still in the accumulation phase, the key questions are:
Making UK pension contributions while in the US:
You need relevant UK earnings (income from UK employment or self-employment) to make UK pension contributions above the £3,600 basic amount rule. If you are employed in the US with no UK earnings, you cannot make meaningful UK pension contributions. However, if you have a UK employer making contributions on your behalf under a UK employment contract, that may count.
Making US pension contributions while UK resident:
US employer 401(k) contributions to a US plan from a UK-based role are unusual. If you are employed in the US and contributing to a 401(k), those contributions should be recognisable for UK tax purposes under DTA Article 18, which provides for pension contributions to be treated consistently with how they are treated in the country of employment — but this analysis is complex and depends on individual circumstances.
IRA contributions while non-resident for US purposes:
If you leave the US and lose US tax residency, you may no longer be able to contribute to a US IRA unless you have US earned income.
Planning for Retirement Across Both Systems
When drawing retirement income from both a UK pension and a 401(k)/IRA, the following considerations apply:
Country of residence at the time of drawing determines primary tax liability — US residents pay US tax on UK pension income (with possible foreign tax credit for UK tax deducted at source), and UK residents pay UK tax on US retirement distributions.
US persons pay US tax regardless of residence — a US citizen living in the UK pays UK tax on UK pension income (as a UK resident) and also reports that income to the IRS (as a US person), then claims a foreign tax credit to offset the double taxation. The credit mechanism generally prevents true double taxation but creates compliance complexity.
Sequencing decisions — the order in which you draw from each pot, and at what ages, can affect lifetime tax significantly. Models should account for RMD requirements on 401(k)/IRA (from age 73 under current rules), which may force distributions whether or not they are tax-efficient.
Social Security and State Pension — both countries have their own state retirement benefit systems. The UK-US Totalization Agreement allows contribution periods to be combined to meet eligibility thresholds, but each country pays its own benefit on its own formula. Both benefits are taxable in the country of residence (with saving clause complications for US persons).
Compliance Caveat
This guide is for general informational purposes only. UK and US pension law, the provisions of the UK-US DTA, IRS rules on foreign pension reporting, and FBAR/FATCA requirements are complex and subject to change. Nothing in this guide constitutes legal, tax, or financial advice. Individuals with UK-US pension positions should seek advice from a tax professional qualified in both jurisdictions. The value of investments within pension plans can fall as well as rise.
How Global Investments Can Help
Global Investments advises internationally mobile clients on pension strategy across multiple jurisdictions, including the UK-US corridor. We understand the tension between US citizenship-based taxation and UK residence-based rules, and we work with dual-qualified advisers who can navigate both systems simultaneously.
Whether you are approaching retirement with both a UK pension and a US 401(k) or IRA, planning contributions during a period of US-UK mobility, or trying to understand your FBAR and FATCA obligations in respect of UK pension accounts, we can help you identify the right approach and connect you with appropriately qualified professionals. Contact us to arrange a confidential conversation.
This guide is for general information only and does not constitute financial, legal or tax advice. Pension rules, tax rates and programme details change; verify current requirements with a qualified and FCA-regulated pensions adviser before acting. Pension transfers involving defined benefits over £30,000 require regulated advice.