ISA US Tax Reporting: What Americans in the UK Must Declare

ISA US tax reporting: an introduction

For ISA US tax reporting, the key point is simple: the US does not recognise the ISA's tax-free status. If you are a US citizen or green card holder, you report ISA interest, dividends and gains on your US return. You also list each ISA on the FBAR and, above the thresholds, on Form 8938. A stocks and shares ISA holding UK funds usually brings PFIC reporting on Form 8621 as well.

This article explains each type of ISA and each form. For the wider picture of reporting UK accounts, read our guide to FBAR and FATCA reporting. It covers every type of foreign account an American in the UK is likely to hold.

Why ISA US tax reporting catches people out

An ISA is an Individual Savings Account: a UK account in which savings and investments grow free of UK tax. UK banks and platforms promote them heavily, and they need no UK tax return entry. Consequently, many Americans open one without thinking about the US side. In our experience, ISAs are among the most common items missing from US returns filed from the UK.

What types of ISA are there?

There are four types of adult ISA: cash, stocks and shares, innovative finance and Lifetime. Each counts towards one annual allowance.

The annual allowance for 2026/27

The GOV.UK page on Individual Savings Accounts sets the maximum at £20,000 for the 2026 to 2027 tax year. You can split it between ISA types. To open or pay into an ISA, you must generally be 18 or over and resident in the UK. Therefore, if you leave the UK, you can usually keep an ISA but cannot add new money.

Budget 2026 and the cash ISA limit

A planned cut to £12,000 a year in cash ISAs for under-65s from April 2027 had been announced and legislated. However, the Budget 2026 overview of tax legislation and rates, published on 28 October 2026, reverses it. The government says it will keep the cash ISA limit at £20,000 for all savers over 18. The legislation to do this is due to be laid in November 2026.

Lifetime and Junior ISAs

The GOV.UK page on the Lifetime ISA allows up to £4,000 a year within the £20,000 limit. The government adds a 25% bonus, up to £1,000 a year. You must open one before age 40. Separately, the Junior ISA limit for children is £9,000 for 2026/27.

How is a cash ISA treated on your US return?

Interest from a cash ISA is taxable US income, reported on Form 1040 like any other bank interest. The UK exemption does not carry over to the US.

The treaty does not protect ISAs

The US-UK income tax treaty, on the IRS UK tax treaty documents page, contains no provision for ISAs. Moreover, its saving clause lets the US tax its citizens largely as if the treaty did not exist. Therefore, ISA income is taxed in the US as ordinary investment income. Our guide to the US-UK double taxation treaty explains the saving clause.

Reporting the interest

IRS Publication 550 says US citizens report investment income from outside the US whether or not they receive a Form 1099. Cash ISA interest is therefore reported in full, converted into dollars. Because no UK tax was paid on it, there is no foreign tax credit to offset it. However, spare credits from UK tax on other income in the same category may sometimes help.

Why the amounts are often small

For many savers, the US tax on cash ISA interest is modest. Nevertheless, it must be reported, and missing it can make a return inaccurate. Additionally, the ISA still counts towards your FBAR and Form 8938 totals. ISA US tax reporting is therefore as much about disclosure as about tax.

Records to keep for ISA US tax reporting

Keep every annual statement and the interest credited each month or quarter. The UK tax year ends on 5 April, but the US year ends on 31 December. Therefore, your provider's annual summary rarely matches the figure your US return needs. Good records make ISA US tax reporting quicker and more accurate each year.

Why is a stocks and shares ISA harder?

A stocks and shares ISA usually holds UK funds, and most UK funds are passive foreign investment companies for US purposes. That brings harsh default tax rules and annual Form 8621 filings.

What a PFIC is

A passive foreign investment company, or PFIC, is a foreign corporation that mainly earns or holds passive income. Under section 1297 of the tax code, it is a PFIC if 75% or more of its gross income is passive. Alternatively, it is one if at least 50% of its assets produce passive income. UK funds structured as companies, such as OEICs, usually meet the test. Unit trusts need checking case by case.

The three tax regimes

The Form 8621 instructions describe three regimes. By default, the excess distribution rules under section 1291 tax gains at the highest rate with an interest charge. Alternatively, a qualified electing fund election taxes your share of the fund's income each year. A mark-to-market election taxes yearly changes in value. Each has drawbacks, and most UK funds do not provide the statements a QEF election needs.

The Form 8621 de minimis rule

The Form 8621 instructions include an exception from Part I of the form. It applies if all your PFIC stock is worth $25,000 or less at the end of the tax year, or $50,000 on a joint return. However, it applies only where there was no excess distribution and no gain treated as one. Therefore, it does not help in a year you sell or receive large distributions. Our article on PFICs and UK funds covers this in depth.

Individual shares inside an ISA

If your stocks and shares ISA holds individual company shares or US-listed funds, the position is simpler. Dividends and gains are reported on your US return as normal. US-domiciled funds are not PFICs. However, many UK platforms restrict US funds for retail investors. Therefore, check what you actually hold before deciding how ISA US tax reporting applies to you.

Selling funds inside the ISA

Switching between funds inside an ISA is tax-free in the UK. For US purposes, however, each sale of a PFIC is a disposal. Under the default rules, a gain on that sale is treated as an excess distribution, taxed at the highest rate with an interest charge. Therefore, frequent switching inside a stocks and shares ISA can create a heavy US reporting burden, even when the UK sees nothing at all.

Do ISAs go on the FBAR and Form 8938?

Yes. An ISA is a foreign financial account for the FBAR, and it is a specified foreign financial asset for Form 8938 once you pass the thresholds.

The FBAR

The FBAR rule is in 31 CFR 1010.350, which covers bank and securities accounts at foreign institutions. A cash ISA is a savings account, and a stocks and shares ISA is a securities account. Neither FinCEN nor the IRS names ISAs specifically, but the definitions clearly reach them. The FinCEN FBAR page says you file when your accounts together exceed $10,000 at any time in the year.

Form 8938

The IRS comparison of Form 8938 and FBAR requirements sets the thresholds for people living abroad. A single filer reports above $200,000 at year end or $300,000 at any time. For a joint return, the figures are $400,000 and $600,000. Moreover, the Form 8938 instructions say assets reported on a timely Form 8621 need not be repeated in detail, though they still count towards the threshold.

Lifetime ISAs and the bonus

A Lifetime ISA is reported like any other ISA on the FBAR and Form 8938. The US treatment of the 25% government bonus is less clear. No IRS guidance addresses it, and practitioners differ. Many treat the bonus as taxable income when it is credited, which is the cautious approach. The GOV.UK guide to withdrawing from a Lifetime ISA sets out the 25% charge on most early withdrawals.

Budget 2026 changes to the Lifetime ISA

Budget 2026 cuts the withdrawal charge from 25% to 20% from 29 October 2026, but only for homes above the property price cap. Other early withdrawals stay at 25%. It also announces a new First Time Buyer ISA to replace the Lifetime ISA for new savers, planned for April 2029. Existing holders keep their accounts under the current rules.

What if you have not reported your ISAs?

If you have left ISAs off past US returns or FBARs, you should correct it. The safest route for a genuine mistake is usually the Streamlined procedures.

Why a late FBAR alone is not enough

The IRS removed its Delinquent FBAR Submission Procedures page in July 2026. Therefore, a late FBAR on its own is no longer a published penalty-free route. Furthermore, missing ISA income usually means the tax returns were wrong too. The Streamlined procedures correct the returns, the FBARs and any Form 8621s together. Our guide to IRS Streamlined filing explains the route.

Catching up on PFIC filings

Missing Forms 8621 can keep the statute of limitations open for the whole return. Consequently, PFIC catch-up work is often the largest part of an ISA correction. The default excess distribution rules can also produce a larger bill than expected. Getting the funds' history together early makes the work faster.

Leaving the UK with an ISA

If you move back to the US, you can usually keep your ISA, but you cannot pay new money in. The UK tax exemption continues for the ISA itself. However, the US reporting continues unchanged, including the FBAR and any Form 8621. Consequently, many returning Americans review their ISAs before they leave, so the US position is clear.

A worked example of ISA US tax reporting

Consider a typical case. Emma and her husband are both US citizens living in Leeds, and they file a joint US return. Emma has a cash ISA and a stocks and shares ISA holding two UK index funds. This is an illustrative example, not a real client.

Emma reports the cash ISA interest on her US return. Both ISAs go on her FBAR, because her accounts together pass $10,000. The couple's total assets stay below $400,000 at year end and $600,000 at any time, so no Form 8938 is needed. Each UK fund is a PFIC. Her PFIC holdings stay under $50,000 and she had no excess distribution, so the Part I exception applies this year.

What Emma's case shows

Emma's ISA US tax reporting is manageable because her holdings are modest. However, when she sells a fund, the excess distribution rules apply and a full Form 8621 is needed. Therefore, she keeps records of each purchase. Additionally, if she stops paying into the stocks and shares ISA, her future savings can go into investments that are simpler on both returns.

How US UK Tax Experts can help

US UK Tax Experts prepares your US and UK returns together, from one file. For ISAs, we prepare the interest and dividend reporting, the FBAR, Form 8938 and each Form 8621. We do not recommend investments. However, we can model the US tax on what you already hold. Our PFIC reporting service and FBAR and FATCA service explain what we prepare.

Conclusion

ISA US tax reporting follows one rule: the US ignores the UK tax wrapper. Cash ISA interest is US income, and stocks and shares ISAs holding UK funds bring PFIC rules. Every ISA belongs on the FBAR once your accounts pass $10,000, and on Form 8938 above the thresholds. Budget 2026 keeps the cash ISA limit at £20,000 and changes the Lifetime ISA, but none of that alters the US position.

Contact us

If you need help with ISA US tax reporting, email hello@usuktaxexperts.com or use our contact form. Tell us which ISAs you hold, what is in them and which years you have filed. We reply within one working day.