ISA Tax Rules for Americans Living in the UK
An ISA is completely free of UK tax, but the IRS does not recognize that status, so the interest, dividends, and gains inside your ISA are taxable on your U.S. return. The IRS requires U.S. citizens abroad to report worldwide income, whether or not it is sheltered in the country where you live. Most people find that the Foreign Tax Credit covers the difference, so reporting matters more than the final bill.
The UK is tightening its own ISA rules as well. Draft regulations published by HMRC on 16 July 2026 cut the annual Cash ISA limit to £12,000 for savers under 65 from 6 April 2027, block transfers into Cash ISAs, and tax interest on cash held inside a Stocks and Shares ISA.
- Every type of ISA is reportable to the IRS. Interest, dividends, and gains all go on your U.S. return
- Stocks and Shares ISAs carry the most work. UK funds inside them are usually Passive Foreign Investment Companies, which means a Form 8621 for each fund
- This tax year, nothing has changed. The full £20,000 can still go into cash, and cash interest inside an investment ISA is untaxed
- From 6 April 2027, the cash limit is £12,000 for under-65s, and cash interest in an investment ISA is taxed at 22%
Here is what applies this tax year, what changes next year, and how to decide whether your ISA still earns its place.
Review Your ISA Before the Rules Change
The Cash ISA Limit Drops to £12,000 in April 2027
From 6 April 2027, savers aged 64 and under can put £12,000 a year into a Cash ISA instead of £20,000. Savers aged 65 and over keep the full £20,000. The overall ISA allowance stays at £20,000 for everyone. The HMRC consultation on the draft rules closes at 11:59 pm on 2 August 2026.
| Rule | This tax year | From 6 April 2027 |
|---|---|---|
| Total ISA allowance | £20,000 | £20,000, no change |
| Cash ISA limit | £20,000, all ages | £12,000 if you are 64 or under |
| Transfers into a Cash ISA | Allowed from any ISA type | Blocked from investment ISAs if you are 64 or under |
| UK tax on cash interest in an investment ISA | None | Savings basic rate, 22% |
Nothing changes mid-year. Money already inside a Cash ISA stays there at any age, and subscribing before 6 April 2027 uses the higher limit while it lasts.
The new charge is the part most easily missed. Under the draft legislation, a new regulation 22A removes relief on interest paid on cash held inside a Stocks and Shares or Innovative Finance ISA. Your provider pays HMRC income tax at the savings basic rate on that interest, and you cannot reclaim it. Because savings rates rise by two percentage points starting in April 2027, the rate becomes 22%. Your provider settles it directly, so it will not appear on your UK Self Assessment return, though you will need the figure for your U.S. return.
For a U.S. taxpayer, the charge lands on top of reporting you were already doing, one more place where UK and U.S. rules treat the same money differently. If you are 65 or over, none of the restrictions apply to you, and our guide to retiring in the UK covers how ISAs sit alongside pensions.
Cash ISA Interest Is Ordinary Income to the IRS
The IRS treats a Cash ISA as an ordinary foreign bank account. Interest is taxable in the year it is earned, whether or not you withdraw it, and you report it on Schedule B. Cash ISAs do not bring PFIC or foreign trust reporting, because they hold deposits rather than funds.
Example: Emma, a U.S. citizen in London, earns £800 of Cash ISA interest and pays £0 in UK tax. She reports roughly $1,020 as ordinary income. After the standard deduction and the Foreign Tax Credit on her other UK-taxed income, she owes no additional U.S. tax. The reporting is required; the bill is not.
Stocks and Shares ISAs Bring PFIC Reporting
A Passive Foreign Investment Company is any foreign pooled investment that covers UK funds, unit trusts, OEICs, investment trusts, and Ireland-domiciled ETFs. Nearly everything inside a typical Stocks and Shares ISA is a PFIC, and each one needs its own Form 8621 every year.
Under the default method, gains are taxed at the highest ordinary rate of 37% rather than long-term capital gains rates, with an interest charge added for each year you held the fund.
Example: Tom holds three UK funds worth £40,000 in a Stocks and Shares ISA. In the UK, the growth is tax-free. For the IRS, he files three Form 8621s a year, and on sale, his gains are taxed at up to 37%. For a portfolio that size, the annual cost of preparing those tax forms can exceed what the wrapper saves him.
Two elections can improve the treatment. The Qualified Electing Fund election is usually unavailable because UK providers rarely issue the PFIC statements the IRS requires. Mark-to-Market can work when the fund trades on a recognized exchange, but it must be elected in the first year you hold it. Our answer on how PFIC rules apply to a UK ISA covers the mechanics.
Individual Shares Stay Outside the PFIC Rules
PFIC status attaches to the fund itself, regardless of where you hold it. Direct ownership of individual company shares is not a PFIC, so holding shares rather than funds maintains the UK tax shelter without the annual Form 8621 filing.
| What you hold in the ISA | PFIC status | U.S. reporting |
|---|---|---|
| Individual UK or U.S. shares | Not a PFIC | Dividends and gains reported normally |
| U.S.-registered funds and ETFs | Not a PFIC | Normal, though rarely on UK platforms |
| UK or Ireland-domiciled funds and ETFs | PFIC | Form 8621 for each fund |
Registration determines PFIC status, not what the fund invests in. A U.S.-registered international index fund is not a PFIC; an Ireland-domiciled fund tracking the same index is.
Most UK platforms let you hold U.S.-listed shares in an ISA. UK savers who are not U.S. persons file a W-8BEN to claim the 15% dividend withholding rate under the U.S.-UK tax treaty. As a U.S. citizen, you file a W-9 instead, and your U.S.-source dividends are taxed as ordinary U.S. income. Some platforms limit accounts for U.S. persons, so it is worth asking your provider first.
The wrapper is also what shelters those dividends from UK tax. Outside an ISA, UK dividends above the £500 allowance are taxed at 10.75%, 35.75%, or 39.35% following the rise on 6 April 2026. Inside one, you pay none of it. For the IRS, dividends from individual companies are generally treated as qualified dividends and taxed at 0%, 15%, or 20%.
Your ISA Counts Toward FBAR and FATCA Limits
Once your foreign accounts total more than $10,000 at any point in the year, a few extra tax forms apply. Your ISA counts toward both thresholds alongside your current account, savings, and pensions.
| Report | Threshold | Form |
|---|---|---|
| FBAR | $10,000 across all foreign accounts, at any point in the year | FinCEN Form 114 |
| FATCA, single filers abroad | $200,000 at year’s end or $300,000 at any point | Form 8938 |
| FATCA, married filing jointly abroad | $400,000 at year’s end or $600,000 at any point | Form 8938 |
Most Americans in the UK reach the FBAR threshold once a UK bank account and an ISA are combined. UK pensions and SIPPs count too, and our guide to UK pensions and U.S. tax covers how they are treated. Separately, an ISA held through a trust arrangement can require Form 3520 foreign trust reporting. Cash ISAs held directly with a bank generally do not, and your provider can confirm the structure.
Keeping an ISA Depends on What It Holds
An ISA holding cash or individual shares usually stays worth having. An ISA holding UK funds is where the numbers often stop working, because the yearly PFIC reporting can cost more than the UK savings.
Usually worth keeping:
- A Cash ISA with a modest balance, where reporting is interest plus FBAR and FATCA
- An ISA holding individual shares, with no PFIC classification and no Form 8621
- Any ISA if you are 65 or over, since your £20,000 cash limit and transfer rights continue
Usually worth restructuring:
- An ISA holding UK funds, where yearly reporting costs can exceed the UK benefit
- Several ISAs across providers, since every fund in every account is its own Form 8621
- Cash inside an investment ISA, which from April 2027 is taxed at 22% with no reclaim
If you are weighing whether the ISA still earns its place, Greenback can model the U.S. and UK cost side by side before you move anything. Learn more about how we help Americans living in the UK, or start with our informational guide on living in the UK.
Leaving the UK Ends Contributions, Not Reporting
Once you are no longer a UK resident, you cannot contribute, open a new ISA, or transfer between types. You can keep existing accounts if your provider allows it, and withdraw without UK tax. U.S. reporting continues through income, FBAR, FATCA, and Form 8621. Selling a fund-holding ISA triggers the PFIC calculation on any gain, so timing is worth planning. If your move is still ahead, our guide to moving to the UK from the U.S. covers the tax steps to take first.
Frequently Asked Questions
No. An ISA is free of UK tax, but the IRS does not treat it as tax-sheltered, so interest, dividends, and gains inside it are taxable on your U.S. return. Our answer on whether a UK ISA is U.S. tax-exempt covers the short version.
Not the overall allowance. From 6 April 2027, the total stays at £20,000, and Cash ISA subscriptions are capped at £12,000 if you are 64 or under at the end of the tax year. Savers 65 and over keep a £20,000 cash limit.
Yes, from 6 April 2027. Your provider pays HMRC income tax at the savings basic rate of 22% on interest paid on cash held in a Stocks and Shares ISA or Innovative Finance ISA, and it cannot be reclaimed.
Yes, by holding individual company shares rather than funds. Direct share ownership is not a PFIC, whether the shares are UK or U.S.-listed, so you keep the UK shelter without filing Form 8621.
Yes. Greenback prepares U.S. returns, including Form 8621, FBAR, and FATCA reporting, and offers UK filing through our in-house UK Chartered Accountant, so both returns line up. Our UK tax services page covers what is included.
The IRS Streamlined Filing Procedures let you catch up on three years of returns and six years of FBARs, often with no penalties where the failure was non-willful. Our guide to Streamlined Filing walks through the eligibility criteria.
Review Your ISA Before the New Rules Start
The 2027 changes are a good reason to look at your ISA properly rather than leave it running. Our CPAs and Enrolled Agents have deep expertise in cross-border investment reporting, including Form 8621, foreign trusts, FBAR, and FATCA, and we can tell you where you stand before anything needs to move. To talk it through, contact our Customer Champions.
Handle Your UK and U.S. Taxes the Right Way
This article is for informational purposes only and does not constitute tax, legal, or financial advice. The UK changes described here are based on draft legislation published for consultation and may change before taking effect. ISA treatment under U.S. tax law depends on your account structure, the investments held, and your circumstances. Rules in both countries change frequently. Always consult a qualified tax professional with expertise in cross-border reporting about your situation.
Featured In
