Topic · United Kingdom
The UK SIPP and US tax: a pension, which is not the same as an exemption
Unlike an ISA, a SIPP is a pension — so the US–UK treaty is genuinely in play. That makes the analysis better, and also less certain. This page separates what is settled from what is a position.
By Danilson Ramos · Founder, Atamatax
Updated August 2026
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Americans in Britain are often told two opposite things about a SIPP: that the treaty makes it invisible until you draw it, and that it is a PFIC minefield the IRS will punish you for. Neither is a good description. A SIPP is a pension, which puts real treaty machinery in play; that machinery is fact-specific, and the honest version of this answer separates the parts that are settled from the parts that are a position you take and can be asked to defend.
Three questions, not one
| The question | What is reasonably settled | What is a position |
|---|---|---|
| Is the SIPP reportable? | Yes — as a foreign financial account and, on its own thresholds, as a specified foreign financial asset | Nothing. Reporting does not depend on the income answer |
| Are UK employer contributions US income now? | The treaty contains machinery addressing contributions to a pension scheme in the other state | Whether your scheme and your facts meet its conditions |
| Is growth inside the SIPP deferred? | The treaty addresses the taxation of pension scheme income | Whether it defers YOUR scheme's growth, and whether disclosure is required |
| Are the funds inside PFICs? | UK and Irish pooled funds generally meet the §1297 tests on their own terms | Whether a pension-wrapper argument removes the Form 8621 obligation |
| Are withdrawals taxable? | Pension distributions are addressed by the treaty's pension article | How the UK's 25% tax-free lump sum interacts with it |
Why the ISA answer does not transfer
It is tempting to reason from the ISA — the UK exemption is ignored, therefore everything British is ignored. That reasoning fails here, and understanding why is what keeps you from over- or under-reporting. An ISA is a general savings wrapper with no US analogue and no treaty article that reaches it. A SIPP is a retirement arrangement, and US treaties contain articles built specifically for retirement arrangements. The category difference is the whole point.
That is a reason for optimism, not for confidence. The articles that could help have conditions, and whether a particular SIPP satisfies them depends on how the scheme is constituted, who contributed, when, and what you elect to do. This is the kind of question where a page that gives you a flat yes is telling you something it cannot know.
The 25% tax-free lump sum
The UK permits a portion of a pension to be drawn free of UK tax. That is a UK rule about UK tax. Whether the same payment is free of US tax is a separate question governed by the treaty and by the saving clause, and it is one of the most commonly over-claimed positions in this area. Treat a confident 'the lump sum is tax-free' as a claim needing support, not as background knowledge.
The funds inside
A SIPP is self-invested, and what people invest it in is usually UK OEICs, unit trusts and Irish-domiciled UCITS ETFs — non-US pooled vehicles that generally meet the §1297 tests. Some practitioners argue that holdings inside a qualifying pension are outside the PFIC shareholder rules; others do not accept it. This is a genuinely contested point, and the responsible thing is to say so rather than pick the answer that produces less work.
What to do with an existing SIPP
- Establish the scheme type: personal SIPP, transferred workplace scheme, or defined-benefit deferred pension. They are not the same arrangement.
- List who contributed and when — your contributions, employer contributions, and any transfers in.
- Pull the holdings with ISINs, and separate pooled funds from cash and direct equities.
- Report the account: it counts toward the FBAR aggregate and toward Form 8938 on its own thresholds, whatever the income analysis concludes.
- Identify which treaty position, if any, you intend to rely on — and get it reviewed before it goes on a return rather than after.
- Keep the position and its basis in writing, because a position you cannot explain in three years is worse than no position at all.
Get the reportable facts straight first
Whatever the treaty answer turns out to be, the account and its holdings still have to be identified. The free checker flags the pooled funds inside your SIPP so the review starts from real data.
Authorities cited
- US–UK Income Tax Treaty — Convention between the United States and the United Kingdom (signed 2001) and the 2002 Protocol
- HMRC · personal pension tax relief — HM Revenue & Customs — Tax on your private pension contributions (relief, annual allowance)
- IRS Form 8833 — About Form 8833 — Treaty-Based Return Position Disclosure Under Section 6114 or 7701(b)
- IRC §1297 — IRC §1297 — Definition of a passive foreign investment company
- IRS Form 8621 — About Form 8621 — Information Return by a Shareholder of a PFIC or QEF
- 31 CFR §1010.350 — 31 CFR §1010.350 — FBAR (FinCEN Form 114) filing requirement and $10,000 threshold
- FinCEN Form 114 (FBAR) — Report of Foreign Bank and Financial Accounts (FBAR)
- IRS Form 8938 — About Form 8938 — Statement of Specified Foreign Financial Assets
- IRC §6038D — IRC §6038D — Information reporting of specified foreign financial assets (Form 8938)
Primary sources (Cornell Legal Information Institute for the US Code and CFR; IRS.gov for forms, procedures, and treaty documents). This page is general information, not individualized tax or legal advice.
Atamatax provides tax preparation support and educational resources. This website does not constitute legal or tax advice.