US Tax on UK Pensions & SIPPs: A Guide for Americans Abroad

Reviewed by a CPA / Enrolled Agent. Last updated: 12 August 2026.

US tax on UK pensions rests on one principle: as a US person you are taxed on worldwide income, yet the US–UK tax treaty generally lets investment growth inside a UK workplace pension or SIPP stay tax-deferred until you draw it. Reporting duties, though, apply from the first year — and they are where most Americans in the UK come unstuck.

This guide explains how the IRS treats UK workplace pensions and SIPPs, the role of the treaty, the 25% tax-free lump sum, what you must report, and the PFIC trap that catches SIPP investors. It is general information, not advice on your return — every UK pension is signed off by a licensed professional before we file.

Key takeaways

• The US–UK treaty generally allows tax-deferred growth in UK pensions to be respected, so you usually are not taxed each year on gains you cannot yet access.
• Employer and employee contributions can be treated differently, and the treaty's protection is not automatic — positions often have to be claimed and disclosed.
• The UK's 25% tax-free lump sum is not guaranteed to be tax-free in the US; the treaty position is unsettled and needs professional judgement.
• Reporting is separate from tax: most UK pensions and SIPPs are reportable on the FBAR and often Form 8938, and some arrangements raise Form 3520 questions.
• A SIPP holding UK funds can expose you to punitive PFIC rules on the underlying investments, even inside the pension.

How does US tax on UK pensions work?

The United States taxes its citizens and green-card holders on their worldwide income, wherever they live. That means your UK pension is on the IRS radar even though it sits in a UK scheme regulated in the UK. Left to domestic US law alone, the growth inside a foreign pension could be taxable to you every year — a harsh result for a retirement pot you cannot touch for decades.

This is exactly the problem the US–UK income tax treaty exists to solve. In broad terms, the treaty coordinates how each country taxes cross-border pensions so that a UK scheme recognised for UK tax purposes can also be respected by the US, deferring US tax on the internal growth until benefits are paid. Understanding US tax on UK pensions therefore starts with the treaty, not with the raw domestic rules.

Does the US–UK tax treaty defer tax on pension growth?

Generally, yes. The pension provisions of the US–UK treaty are designed to let the build-up of value inside a qualifying UK pension grow without an annual US tax charge, broadly mirroring the tax deferral the UK already gives. When you eventually draw an income, that income is brought into charge, and the treaty and foreign tax credit rules work together to stop the same money being fully taxed twice.

Three cautions matter here. First, treaty relief is not automatic — the position often has to be claimed on your return, and some positions must be disclosed (for example on Form 8833). Second, the treaty's benefits depend on the scheme actually qualifying as a pension under its terms — not every arrangement labelled a "pension" fits neatly. Third, the exact article references and mechanics turn on current treaty text and IRS guidance, so confirm the specifics against the primary source and a professional before you rely on them. You can read the treaty and its technical explanation on the IRS's UK tax treaty documents page.

Are employer and employee contributions taxed differently?

They can be, and the distinction matters more than most people expect. Broadly, the treaty is intended to prevent employer contributions to a qualifying UK workplace pension from being treated as immediately taxable US income to you, and to allow your own contributions to be recognised within limits similar to those the US gives its own retirement plans. In practice, that means an ordinary auto-enrolment workplace pension is usually the most straightforward case.

The picture gets more complex with generous employer schemes, salary-sacrifice arrangements, and personal contributions to a SIPP, where the interaction between UK relief and US limits needs careful mapping. The goal is to line up UK and US treatment so contributions are not taxed on the way in and then again on the way out. Because the answer is fact-specific, this is one area where a quick professional review pays for itself.

Is the UK's 25% tax-free lump sum tax-free in the US?

This is the single most misunderstood point for US expats in the UK. Under UK rules, you can usually take part of your pension — commonly up to 25%, within UK limits — as a tax-free lump sum. It is genuinely tax-free in the UK. It does not follow that the IRS sees it the same way.

The US treatment of a UK pension lump sum is genuinely unsettled. Some advisers take a treaty position that such a lump sum is exempt from US tax; others treat all or part of it as a taxable pension distribution in the US. Getting this wrong is expensive in both directions — an unnecessary US tax bill, or an under-reported distribution that surfaces later. If a tax-free lump sum is on your horizon, treat it as a decision to plan in advance, not a form to complete afterwards. The UK side of the rule is summarised on GOV.UK's tax on your private pension guidance.

What do I have to report — FBAR, Form 8938 and Form 3520?

Reporting is where compliance most often breaks down, because it is separate from whether any tax is due. Filing these forms does not create a tax charge — but failing to file them can create serious penalties. For most Americans with a UK pension or SIPP:

• FBAR (FinCEN Form 114): if your foreign financial accounts together exceed $10,000 at any point in the year, you generally report them — and many UK pensions and SIPPs count. See the IRS FBAR guidance.
• Form 8938 (FATCA): depending on your filing status and where you live, a pension may also need reporting here, with thresholds that differ from the FBAR. The IRS Form 8938 pages set out the comparison.
• Form 3520 / 3520-A: some foreign pension arrangements are technically foreign trusts, which can raise these forms. Relief exists for certain tax-favoured foreign retirement trusts, but whether it applies to your scheme is a professional call, not an assumption.

The practical rule: report first, worry about tax second. A disclosed pension almost never creates a problem; an undisclosed one can.

Is my SIPP a PFIC?

SIPPs give you investment freedom, and that freedom is exactly where the risk lies. The SIPP wrapper itself is generally not a passive foreign investment company (PFIC). But the funds inside it very often are. Most UK-domiciled OEICs, unit trusts and ETFs are PFICs for US purposes, and PFIC rules can impose punitive tax and interest plus annual Form 8621 filing.

Whether the pension wrapper shields those holdings from PFIC treatment depends on the facts and any treaty protection available — it is not something to assume in either direction. If you hold, or plan to hold, non-US funds in a SIPP, the underlying investments deserve as much attention as the pension itself. We cover this in depth in our companion guide to PFIC tax rules for US investors abroad.

Getting your UK pension right with the IRS

US tax on UK pensions is not impossible to get right — but it rewards planning and punishes guesswork. The treaty is generous where it applies, the reporting is unforgiving where it is missed, and the lump-sum and PFIC questions are genuinely technical. If you have a meaningful UK pension or SIPP, a considered, professionally signed-off position is worth real money.

If you have fallen behind, there is a clean route back: our guides on missed US tax returns and the IRS Streamlined Foreign Offshore Procedures explain how many expats catch up without the worst penalties. And if you would rather have a specialist handle it, our US–UK expat tax accountants work with Americans in the UK every day. Every return is prepared to a ready-to-sign standard and reviewed by a licensed CPA or Enrolled Agent before anything is filed — book a consultation to talk through your pension position.

Frequently asked questions

Do I have to pay US tax on my UK pension every year?

Generally no. The US-UK tax treaty allows the investment growth inside a UK workplace pension or SIPP to be respected as tax-deferred, so you usually are not taxed year by year on gains you cannot yet access. US tax typically arises when you draw benefits. Because the treaty is not self-executing in every situation, a professional should confirm your specific position and whether a treaty position needs to be disclosed on your return.

Is my UK 25% tax-free lump sum tax-free in the US too?

Not necessarily. The UK allows part of a pension to be taken as a tax-free lump sum (commonly 25%, subject to UK limits), but the IRS does not automatically mirror that treatment, and the US treaty position on lump sums is unsettled. Some advisers take a treaty position that a lump sum from a UK scheme is exempt; others treat part of it as taxable in the US. This is a high-stakes judgement call — get it reviewed before you draw the cash.

Do I have to report my SIPP or UK pension on an FBAR?

Usually yes. If your foreign financial accounts, including many UK pensions and SIPPs, together exceed $10,000 at any point in the year, you generally file an FBAR (FinCEN Form 114). Some pensions may also be reportable on Form 8938 depending on your filing status and thresholds. Reporting a pension is a disclosure exercise, not a tax charge — filing it does not itself create US tax.

Is my SIPP a PFIC?

The SIPP wrapper itself is generally not a PFIC, but the funds inside it can be. Most UK-domiciled OEICs, unit trusts and ETFs are passive foreign investment companies for US purposes, which can trigger punitive tax and Form 8621. Whether the pension wrapper shields those holdings depends on the facts and any available treaty relief, so the underlying investments matter as much as the account type.

Does the US-UK treaty stop me being taxed twice on my pension?

It is designed to. The treaty coordinates which country taxes pension income and, combined with foreign tax credits, generally prevents the same income being fully taxed twice. It is not automatic, though — you often have to claim relief correctly on both sides and disclose treaty positions, and mistakes can leave real double taxation on the table.

I have never reported my UK pension to the IRS. What now?

You are far from alone, and there are structured ways back into compliance. Many Americans in the UK use the IRS Streamlined Foreign Offshore Procedures to catch up on missed returns and FBARs without the harshest penalties, where they qualify. The right path depends on your facts — speak to a licensed professional before filing anything.