Pensions Under the US-UK Tax Treaty: Lump Sums, QROPS, and FBAR

The US-UK income tax treaty coordinates how pensions are taxed when contributions, growth, or withdrawals cross the Atlantic. In broad terms, investment growth inside a qualifying pension is not taxed by the other country until money actually comes out, distributions are generally taxable where you live, and lump sums are generally taxable where the pension is based. Those rules sit alongside a Saving Clause that lets the US keep taxing its own citizens on much of the same income, plus a set of US filing forms whose penalties often dwarf the underlying tax. Getting the direction of the pension, your citizenship, and the type of scheme right is what determines the actual outcome.

Which Pensions the Treaty Covers

The pension articles apply to schemes that receive tax-favored treatment under either country’s domestic law. An Exchange of Notes attached to the treaty lists the qualifying plans.

On the US side, that includes qualified plans under IRC §401(a) such as 401(k)s, profit-sharing plans, and defined benefit plans; individual retirement plans including traditional IRAs, SEP-IRAs, SIMPLE IRAs, and Roth IRAs under IRC §408A; and §403(a) and §403(b) annuity plans. On the UK side, it covers registered pension schemes: Self-Invested Personal Pensions (SIPPs), occupational pension schemes, and personal pension plans.

Informal savings arrangements, non-registered investment vehicles, and foreign trusts that don’t meet either country’s definition of a tax-favored retirement plan fall outside the pension articles. If your retirement money isn’t in a scheme that qualifies for tax-advantaged treatment in its home country, the protections below won’t reach it.

Tax on Pension Growth Before You Withdraw

Article 18(1) of the treaty says income earned inside a covered pension scheme can only be taxed when it’s paid out, not while it accumulates. This preserves tax deferral regardless of which country you’re living in. Article 18(1) is one of the provisions explicitly excepted from the Saving Clause, so even US citizens living in the UK keep the benefit for UK pension growth, and UK nationals living in the US keep it for US pension growth.¹

The benefit matters most for UK residents holding US IRAs or 401(k)s. Without the treaty, HMRC’s domestic rules would treat annual dividends, interest, and gains inside the US account as taxable UK income each year, effectively converting a tax-deferred retirement account into an inefficient investment fund. To keep the deferral, you have to actively claim the treaty position with HMRC, typically when you first become UK resident or first hold a US retirement account while UK resident. Miss the claim and HMRC can apply domestic rules, taxing phantom income you haven’t received.

Roth IRAs and Roth 401(k)s are listed among the covered schemes, so the same accumulation-phase deferral applies. What happens at withdrawal is more nuanced and is covered below.

Tax on Pension Distributions

Article 17(1)(a) says periodic pension payments are taxable only in the country where the recipient lives. A US citizen living in the UK who draws from a US 401(k) generally owes UK tax; a UK national living in the US who draws a UK occupational pension generally owes US tax.

Article 17(1)(b) adds a second rule: any amount that would be exempt from tax in the country where the pension is established must also be exempt in the recipient’s country of residence.² HMRC has confirmed that a distribution from a US IRA to a UK resident is exempt from UK tax to the same extent it would be exempt in the US.³

How the Saving Clause Changes the Answer for US Citizens

The Saving Clause in Article 1(4) lets the US tax its citizens and residents on worldwide income as if the treaty didn’t exist. Article 1(5) lists the pension provisions that survive it anyway: Article 17(1)(b), Article 17(3), Article 17(5), and Article 18(1).¹

Notice what’s missing. Article 17(1)(a), the general residence-only rule for periodic payments, is not on the list. So a US citizen living in the UK who draws a UK pension is taxable in both countries: the UK as country of residence, and the US as country of citizenship. To prevent the same income being taxed twice, Article 24 provides a Foreign Tax Credit. In effect, you pay the higher of the two rates, not both stacked together.

Roth Distributions

Qualified Roth distributions are tax-free in the US. Because Article 17(1)(b) requires the residence country to honor a source-country exemption, a UK resident receiving a qualified Roth distribution has a strong treaty argument that the UK should also treat the payment as exempt. Article 17(1)(b) is one of the Saving Clause exceptions, which strengthens the position.² In practice, claiming this treatment with HMRC requires documentation and is worth professional advice.

Lump Sums and the UK 25% Tax-Free Portion

Article 17(2) says a lump sum from a pension scheme is taxable only in the country where the scheme is established.⁴ A lump sum from a UK pension paid to a US resident would, by that rule, be UK-taxable only. But Article 17(2) is not among the Saving Clause exceptions, so the US retains the right to tax its citizens on lump sums from UK pensions.

The UK permits a Pension Commencement Lump Sum (PCLS) of up to 25% of the fund, capped at £268,275, to be taken tax-free.⁵ For a US citizen or resident, Article 17(1)(b) — which does survive the Saving Clause — provides a reasonable argument that this tax-free portion should also be exempt from US tax. Taxpayers claiming that position should file Form 8833 to disclose it.⁶ The IRS has not issued definitive guidance confirming the PCLS qualifies, and the agency has historically scrutinized these claims. The remaining 75% of a UK lump sum has weaker treaty protection for US taxpayers because Article 17(2) itself is not a Saving Clause exception. Cross-border tax advice before taking a UK lump sum is a good idea.

Government Service Pensions

Pensions paid for government service are governed by Article 19, which overrides Article 17. Article 19 is a Saving Clause exception, giving it stronger protection than the general pension rules.

The default rule: a government pension is taxable only in the country whose government pays it. A retired US federal employee living in the UK pays US tax on their federal pension. A retired UK civil servant living in the US pays UK tax on the UK government pension.⁷

Nationality flips the outcome. If the recipient is both a resident and a national of the other country, the pension is taxable only in that country. A US citizen who retired from UK government service and lives in the US would pay US tax on the UK government pension, not UK tax.⁸

Pensions from services connected to a business run by a government, rather than direct government functions, fall back under Article 17.⁸ Whether a specific scheme like the NHS pension falls under Article 19 or Article 17 depends on how HMRC and the IRS classify the underlying service. Confirm the classification before assuming which country taxes it.

UK State Pension and US Social Security

Article 17(3) assigns taxing rights over the UK State Pension and US Social Security to the country where the recipient lives.⁹ A US resident receiving the UK State Pension pays US tax on it. A UK resident receiving US Social Security pays UK tax. Article 17(3) is a Saving Clause exception, so the residence rule holds even for US citizens.

US residents receiving the UK State Pension should factor in the Windfall Elimination Provision (WEP), which can reduce their US Social Security benefit because it’s based on employment where they didn’t pay US Social Security taxes.¹⁰ The reduction isn’t total; 30 or more years of “substantial earnings” under US Social Security eliminates WEP entirely. The Social Security Administration publishes a screening tool for estimating the effect.

Separately, the US-UK Totalization Agreement lets workers combine credits from both systems to qualify for benefits when they don’t have enough in one country alone. You need at least six US credits, roughly eighteen months of work, to draw a partial US benefit using combined credits.¹¹ The Totalization Agreement is a separate instrument from the income tax treaty.

Transferring a UK Pension to a QROPS

Moving a UK pension to a Qualifying Recognised Overseas Pension Scheme in a third country is permitted under UK law, but the IRS treats it as falling outside the treaty. Once assets leave a UK-registered scheme, the transfer is not an “eligible rollover distribution” under IRC §402(c)(4), and the US may treat the full value as a taxable distribution.¹²

Article 18’s deferral only reaches pension schemes “established in the other Contracting State.” Once the money is in a scheme outside both the US and the UK, that protection is gone. A US citizen or green card holder who transfers a UK pension to a QROPS in a third country can face an immediate US tax bill on the full transferred value. Get US tax advice before initiating any such transfer.

Withholding at Source

A US pension plan paying a distribution to a person it knows is foreign must withhold 30% of the gross payment. A UK resident can reduce or eliminate that withholding by filing Form W-8BEN with the plan administrator, certifying UK residency and claiming the treaty benefit.¹³

Going the other way, a UK pension paying a US resident withholds UK tax at the applicable marginal rate. The US resident then claims that UK tax as a Foreign Tax Credit on the US return. The combined effect is that you pay the higher of the two countries’ rates, not the sum.

Forms You Have to File

Treaty benefits aren’t automatic. They depend on filings, and the penalties for missing them regularly exceed the tax at stake.

FBAR (FinCEN Form 114)

US citizens and residents holding a foreign pension must file an FBAR if the combined value of all their foreign financial accounts exceeded $10,000 at any point in the year. A UK pension counts. The FBAR is filed electronically through FinCEN’s BSA E-Filing System, separate from the tax return, and is due April 15 with an automatic extension to October 15.¹⁴ Non-willful violations carry penalties of up to roughly $16,500 per account per year; willful violations can cost the greater of about $165,000 or 50% of the account balance per year.

Form 8938

Form 8938 is a separate foreign asset disclosure filed with your tax return. For US residents filing individually, the threshold is $50,000 on the last day of the year or $75,000 at any point during the year. For filers living abroad, the thresholds rise to $200,000 and $300,000. Joint filers get double.¹⁵ Failure to file carries a $10,000 penalty, plus up to $50,000 for continued noncompliance after IRS notice, plus a 40% penalty on any tax understatement tied to the undisclosed assets.¹⁶

Form 8833

Any treaty position that overrides a provision of the Internal Revenue Code has to be disclosed on Form 8833, attached to the tax return. That includes UK residents claiming the Article 18 deferral on US retirement account growth, US residents claiming the Article 17(1)(b) exemption for the UK PCLS, and any other treaty-based override. The form asks for the treaty article, the IRC section overridden, and the amount of income affected. The penalty for missing it is $1,000 per failure, $10,000 for C corporations, though the IRS can waive it for reasonable cause.⁶

Forms 3520 and 3520-A Relief

A foreign pension is technically a foreign trust under US law, which would normally trigger Form 3520 and Form 3520-A. Revenue Procedure 2020-17 provides relief for eligible individuals with qualifying foreign retirement trusts. A UK registered pension scheme generally qualifies if it is tax-favored in the UK, subject to UK information reporting, and limits contributions to earned income with annual or lifetime caps, among other criteria.¹⁷ Most standard UK workplace pensions and SIPPs meet the criteria, but confirm against the revenue procedure before skipping the forms.

States That Don’t Follow the Treaty

Federal treaties don’t bind US states. Several states, including California, New Jersey, Connecticut, and Pennsylvania, don’t honor federal treaty benefits when calculating state income tax.¹⁸ If you live in one of those states and use the treaty to exclude UK pension income federally, you may have to add it back on the state return. Check with your state tax department before assuming a federal treaty position carries through, particularly for the Article 17(1)(b) exemption or the Article 18 deferral.

Estate Tax on Cross-Border Pension Assets

The income tax treaty doesn’t cover estate tax. A separate US-UK Estate and Gift Tax Treaty coordinates taxing rights at death, using treaty domicile to allocate primary rights and providing credits when both countries tax the same transfer.

UK rules changed on April 6, 2025. Under the current residency-based regime running through April 5, 2027, someone who has been UK resident for 10 of the last 20 years has their worldwide assets, potentially including US retirement accounts, brought into UK inheritance tax at 40% above the £325,000 nil-rate band. From April 6, 2027, unused pension funds including US 401(k)s, traditional IRAs, and Roth IRAs are expected to be fully included in the taxable worldwide estate for long-term UK residents. The estate treaty may provide relief if the deceased qualifies as a US domiciliary under its terms, but the interaction between the estate treaty, UK inheritance tax reform, and US estate tax is genuinely complex. Anyone with significant retirement assets on both sides should review their estate plan with advisors in both countries well before 2027.

1
U.S. Department of the Treasury. US-UK Income Tax Treaty (2001) – Section: Article 1(5)
2
U.S. Department of the Treasury. US-UK Income Tax Treaty (2001) – Section: Article 17(1)(b)
3
HM Revenue & Customs. DT19853 – Double Taxation Relief Manual: United States of America: Notes – Section: Pensions
4
U.S. Department of the Treasury. US-UK Income Tax Treaty (2001) – Section: Article 17(2)
5
GOV.UK. Tax on Your Private Pension Contributions: Lump Sum Allowance
6
Internal Revenue Service. Form 8833 – Treaty-Based Return Position Disclosure
7
U.S. Department of the Treasury. US-UK Income Tax Treaty (2001) – Section: Article 19
8
Internal Revenue Service. Technical Explanation of the US-UK Convention – Section: Article 19
9
The Double Taxation Relief (Taxes on Income) (The United States of America). The Double Taxation Relief (Taxes on Income) (The United States of America) Order 2002 – Section: Pensions, Social Security
10
Social Security Administration. Windfall Elimination Provision and Foreign Pensions
11
Social Security Administration. Totalization Agreement with United Kingdom
12
Internal Revenue Service. Chief Counsel Advice Memorandum AM2008-009
13
Internal Revenue Service. Plan Distributions to Foreign Persons Require Withholding
14
Financial Crimes Enforcement Network (FinCEN). BSA Electronic Filing Requirements For Report of Foreign Bank and Financial Accounts (FinCEN Form 114)
15
Internal Revenue Service. Do I Need to File Form 8938, Statement of Specified Foreign Financial Assets?
16
Internal Revenue Service. Summary of FATCA Reporting for U.S. Taxpayers
17
Internal Revenue Service. Revenue Procedure 2020-17
18
Internal Revenue Service. State Income Taxes