Introduction
You opened a Stocks and Shares ISA at Hargreaves Lansdown because everyone in the UK does. Your employer auto-enrolled you into a workplace pension at NEST or Aviva. You have a SIPP from a previous job. None of this felt unusual — until you read that the IRS treats UK ISAs and pensions very differently from HMRC, and that missed reporting can cost $10,000 per form per year.
This guide is written for Americans living in England, Scotland, Wales, and Northern Ireland, including dual US-UK citizens and Green Card holders, who hold UK pensions or ISAs and want to know exactly what the IRS expects. The IRS Streamlined Procedures are referenced throughout because, for the vast majority of UK-based Americans behind on these filings, they are the cleanest way out. For broader context, see our service page at https://www.taxyork.com/services/.
What Are the IRS Streamlined Procedures?
The IRS Streamlined Procedures are an official IRS amnesty program for taxpayers whose failure to report foreign income, file US returns, or submit FBARs was non-willful — meaning negligence, inadvertence, mistake, or a good-faith misunderstanding of the law.
For Americans living in the UK, the relevant track is the Streamlined Foreign Offshore Procedures (SFOP). It allows you to file three years of late or amended Form 1040 returns, six years of FBARs (FinCEN Form 114), and a non-willfulness certification on Form 14653. In return, the IRS waives all failure-to-file, failure-to-pay, accuracy-related, information-return, and FBAR penalties. The 5% miscellaneous offshore penalty under SDOP does not apply to qualifying UK-based filers.
This matters enormously for ISA and pension holders because almost every American with a UK ISA has under-reported income — even if they correctly filed Form 1040 in every other respect. The official rules are at https://www.irs.gov/individuals/international-taxpayers/streamlined-filing-compliance-procedures.
Who Qualifies — US Expats in the UK Explained
To qualify for SFOP under the IRS Streamlined Procedures, you must meet the non-residency test. In at least one of the last three years for which the US tax return due date has passed, you were physically outside the United States for at least 330 full days, and did not maintain a US abode. Almost every American genuinely living in the UK long-term meets this. You must also certify non-willfulness and not currently be under IRS examination or criminal investigation.
Several misconceptions cause real harm. The US-UK tax treaty does not eliminate your obligation to file Form 1040. PAYE does not replace US filing. Long residence in the UK does not put you under the IRS radar — UK banks and pension administrators report directly to the IRS via HMRC under FATCA. Moreover, UK ISAs are not tax-free for US purposes, regardless of what HMRC says. Confirmation of expat filing rules is at https://www.irs.gov/individuals/international-taxpayers.
UK ISAs and the IRS — The Reporting Most Expats Miss
This is the section most blogs get wrong, so read it carefully.
Cash ISAs
A Cash ISA at Nationwide, Santander, or Marcus is taxable for US purposes. Interest earned inside the wrapper is reportable on Schedule B of Form 1040 every year, even though HMRC ignores it. The ISA itself is reportable on FBAR if your aggregate foreign accounts exceed $10,000, and on Form 8938 if you cross the FATCA thresholds ($200,000 single / $400,000 joint at year-end for UK residents).
Stocks and Shares ISAs — the PFIC Problem
A Stocks and Shares ISA holding UK-domiciled funds is the single biggest IRS trap for Americans in the UK. Almost every UK-listed unit trust, OEIC, or ETF — Vanguard UK funds, iShares UK ETFs, Fidelity UK funds — is classified as a Passive Foreign Investment Company (PFIC) by the IRS.
PFICs trigger Form 8621, one of the most punitive forms in the entire US tax code. Without a timely mark-to-market or QEF election, gains are taxed at the highest ordinary income rate plus an interest charge, and excess distributions are spread back over the holding period with compounding interest. A £15,000 ISA in three Vanguard UK index funds becomes three separate Form 8621 filings every year.
Lifetime ISAs and Innovative Finance ISAs
Lifetime ISAs are treated like Stocks and Shares ISAs for US purposes if held in funds, plus the 25% government bonus is arguably taxable income to the IRS. Innovative Finance ISAs holding peer-to-peer loans are reportable on FBAR and Form 8938, with interest taxable on Form 1040.
The IRS Streamlined Procedures are the right route to fix multiple years of missed ISA reporting. The IRS guidance on PFICs is at https://www.irs.gov/forms-pubs/about-form-8621.
UK Pensions and the IRS — What You Must Disclose
UK pensions are reportable under several regimes simultaneously. A workplace pension at NEST, Aviva, Legal & General, or your employer's scheme is generally reportable on FBAR once you have plan assets over the $10,000 aggregate threshold. It is also reportable on Form 8938 if you cross FATCA thresholds. SIPPs from Hargreaves Lansdown, AJ Bell, or Interactive Investor are reportable in the same way and may also trigger Form 8621 if they hold UK-domiciled funds.
The US-UK Income Tax Convention (1975, as amended) provides meaningful protection here. Article 17 allows US persons to defer tax on UK pension growth and employer contributions until distribution, and Article 18(5) covers cross-border contributions. To rely on these provisions, you typically need to file Form 8833 to make the treaty election in the year you first claim it.
The UK State Pension is treated as US Social Security for treaty purposes under Article 17(3), meaning it is generally taxable only in the UK if you are a UK resident. UK pension lump sums are a particularly nuanced area where the 25% tax-free element is often taxable on the US side despite UK treatment.
Step-by-Step: Catching Up Using the IRS Streamlined Procedures
First, confirm SFOP eligibility — gather travel records, UK tenancy agreements, or HMRC residency confirmation showing 330+ days outside the US.
Second, list every UK financial account: current accounts, savings accounts, ISAs, NS&I products, workplace pensions, SIPPs, and personal pensions, with peak balances for the last six years.
Third, prepare three years of Form 1040 with the right elections — Form 1116 (Foreign Tax Credit) usually beats Form 2555 (FEIE) for UK earners because UK tax rates exceed US rates, and FTC carryovers preserve future value.
Fourth, prepare the information-return stack: Form 8938 for FATCA, Form 8621 for every PFIC inside ISAs and SIPPs, Form 8833 for treaty positions on pensions, and Form 3520 if a foreign pension is treated as a foreign trust.
Fifth, file six years of FBARs through https://bsaefiling.fincen.treas.gov/main.html, marked as filed under Streamlined.
Sixth, draft Form 14653 — the non-willfulness certification, which the IRS reads carefully and which must be specific to your real life. Form 14653 instructions are at https://www.irs.gov/forms-pubs/about-form-14653.
Real UK Expat Scenario — Streamlined in Practice
Sarah, an American teacher in Manchester, contacted TaxYork in early 2026. She had moved to the UK in 2015, joined the Teachers' Pension Scheme, opened a Stocks and Shares ISA with Hargreaves Lansdown holding three Vanguard UK funds, and had been filing her own Form 1040 using TurboTax. She had ticked "no" on Schedule B for foreign accounts and had never filed an FBAR, Form 8938, or Form 8621.
What we identified: six years of missing FBARs, three years of missing Form 8938, three years of missing Form 8621 (three PFICs × three years = nine filings), no Form 8833 election on the Teachers' Pension, and incorrectly elected FEIE when FTC would have been more beneficial.
We filed under SFOP. Three amended Form 1040 returns with Form 1116 replacing Form 2555, three years of Form 8938, nine Form 8621 filings with mark-to-market elections going forward, Form 8833 for the pension treaty position, and six years of FBAR. Outcome: full IRS compliance, zero penalties, a small refund from re-electing the Foreign Tax Credit, and a clean PFIC strategy (she switched the ISA to UK-listed shares of US-domiciled funds). For related reading, see https://www.taxyork.com/blog/.
Key IRS Deadlines for US Expats in the UK — 2026
Deadline
Form / Obligation
Whom does it apply to
Key Note for UK Expats
15 April 2026
Form 1040 standard due date
All US citizens and Green Card holders
UK expats get automatic extension to 15 June
15 June 2026
Form 1040 expat extension
US citizens abroad
No form needed; interest accrues from 15 April on tax owed
15 October 2026
Form 1040 final extension
Anyone filing Form 4868 by 15 June
Final deadline; missing it triggers FTF penalties
15 October 2026
FBAR (FinCEN 114)
Anyone with foreign accounts over $10,000 aggregate
Automatic extension from 15 April — no form needed
15 October 2026
Form 8938 (FATCA)
Higher expat thresholds apply
Filed with Form 1040; follows the same extension
15 October 2026
Form 8621 (PFIC)
Anyone with UK funds inside ISAs or SIPPs
One form per PFIC per year
Current dates are confirmed at https://www.irs.gov/individuals/international-taxpayers/us-citizens-and-resident-aliens-abroad.
Penalties for Non-Compliance
The penalty schedule for missed UK pension and ISA reporting is genuinely punishing. FBAR non-willful penalties are up to $10,000 per form per year. Willful FBAR penalties are the greater of $100,000 or 50% of the account balance per year. Form 8938 carries an initial penalty of $10,000, rising to $50,000 for continued failure. Form 8621 has no specific dollar penalty but keeps the tax year open indefinitely until filed, and triggers excess distribution treatment that can wipe out most of a fund's gains. The Form 3520 penalty for unreported foreign trusts or gifts is 35% of the amount.
This is exactly why the IRS Streamlined Procedures matter so much for ISA and pension holders. For non-willful expats who meet the SFOP non-residency test, all of these penalties are waived. The IRS penalty relief overview is at https://www.irs.gov/payments/penalty-relief.
Common Mistakes Americans in the UK Make
Six mistakes recur in almost every case we see. The first is assuming a UK ISA is tax-free for US purposes — it is not. The second is missing the PFIC classification of UK-domiciled funds and skipping Form 8621. The third is not reporting workplace pensions on FBAR or Form 8938 because "I can't access the money yet" — accessibility is irrelevant to reporting. The fourth is electing FEIE when FTC would have produced better long-term outcomes, given the UK's higher tax rates. The fifth is skipping Form 8833 for treaty positions on pension growth, exposing growth to current US taxation. The sixth is waiting too long to use Streamlined and losing eligibility once the IRS contacts you due to a FATCA mismatch.
The US-UK Tax Treaty — How It Affects Pensions and ISAs
The US-UK Income Tax Convention is genuinely useful but routinely misunderstood. Article 17 governs pensions and is the basis for deferring US tax on UK pension growth and contributions until distribution. Article 18(5) handles cross-border contributions. Article 24 coordinates the UK State Pension with the US Social Security. Article 4 contains the tiebreaker rules for dual residents.
What the treaty does not do: it does not eliminate Form 1040, FBAR, FATCA, or PFIC reporting for US citizens. The saving clause in Article 1(4) preserves the United States' right to tax its citizens regardless of UK residency, with limited carve-outs. Crucially, the treaty does not extend ISA tax-exempt status to the US side — ISAs remain fully taxable for US purposes. The full treaty text is at https://home.treasury.gov/policy-issues/tax-policy/international-tax.
Comparison Table — UK Pension vs UK ISA — IRS Reporting
Reporting Item
UK Workplace Pension / SIPP
Stocks & Shares ISA
Cash ISA
FBAR (FinCEN 114)
Yes, once the threshold is met
Yes, once the threshold is met
Yes, once the threshold is met
Form 8938 (FATCA)
Yes, if expat thresholds met
Yes, if expat thresholds met
Yes, if expat thresholds met
Form 8621 (PFIC)
Yes, it holds UK funds
Almost always yes
No
Form 8833 (treaty election)
Recommended for growth deferral
No
No
Form 3520 (foreign trust)
Sometimes — fact-specific
No
No
Annual income on Form 1040
Generally deferred under Article 17
Yes — every year
Yes — every year
How TaxYork Helps Americans in the UK
TaxYork specializes exclusively in US-UK expat tax matters. Our team includes IRS Enrolled Agents and CPAs authorized to represent taxpayers before the IRS, with day-to-day experience of UK ISAs, workplace pensions, SIPPs, PFIC analysis, treaty elections, and Self Assessment crossovers.
We handle Streamlined Foreign Offshore submissions end-to-end — eligibility analysis, six years of FBAR, three years of returns with proper Form 1116 or 2555 optimization, full Form 8938 and 8621 compliance, Article 17 treaty elections via Form 8833, and the all-important Form 14653 narrative. Contact TaxYork at info@taxyork.com or https://www.taxyork.com — we help Americans in the UK get fully IRS-compliant, almost always with all penalties eliminated through the IRS Streamlined Procedures.
Conclusion
Three things matter most for Americans living in the UK with pensions and ISAs. First, your UK ISA is not tax-free for US purposes, and Stocks and Shares ISAs almost always trigger PFIC reporting. Second, your workplace pension and SIPP need annual FBAR and Form 8938 disclosure, with treaty elections to defer growth. Third, when you have missed years of these filings, the Streamlined Foreign Offshore Procedure is the cleanest, fastest, penalty-free route back to compliance. Contact TaxYork at info@taxyork.com or https://www.taxyork.com — we help Americans in the UK get fully IRS-compliant, almost always with all penalties eliminated through the IRS Streamlined Procedures.