Cash ISA changes 2027: the £12,000 cap and why Americans lose the most

Figures relate to tax year 2027-28 (UK) · 2026 and 2027 (US)

From 6 April 2027, if you are under 65 you can put only £12,000 a year into cash ISAs. The overall allowance stays at £20,000, but the rest must go into an investment ISA. For an American in Britain, the cash ISA changes 2027 bite harder than they do for a British neighbour.

That is because the cash ISA was the one ISA that suited a US person. Its interest is taxable in America anyway. But it holds bank deposits, not funds, so it avoids the harsh American rules on foreign funds. Now that safe slice shrinks by £8,000 a year.

This guide covers the new rules, what they mean for your US return, and where the extra cash can go. Every figure comes from GOV.UK, legislation.gov.uk or the IRS, with its tax year.

Key takeaways

• Under the cash ISA changes 2027, savers aged 64 or under at the end of the tax year can subscribe £12,000 a year to cash ISAs, down from £20,000.
• The overall ISA allowance stays at £20,000 for 2027-28.
• Savers aged 65 or over at the end of the tax year keep a £20,000 cash limit.
• Under-65s will not be able to transfer money from a stocks and shares ISA into a cash ISA.
• Interest on cash held inside a stocks and shares ISA will suffer a flat 22% charge, paid by the ISA manager.
• For a US person, cash ISA interest was always taxable on the American return, with no British tax to credit.
• The cash ISA mattered because it is not a PFIC. Most fund-based stocks and shares ISAs are.
• Savings rates in Britain also rise by two points from April 2027, so money pushed out of the ISA costs more there too.

What are the cash ISA changes 2027?

The cash ISA changes 2027 cut the yearly cash ISA limit to £12,000 for under-65s. They start on 6 April 2027, and the total ISA allowance stays at £20,000. New rules also stop under-65s moving money from investment ISAs into cash. Cash left idle inside an investment ISA will be taxed too.

The change was announced at the Autumn Budget 2025. HMRC then published a policy paper on the cash ISA limit (opens in a new tab) on 17 September 2026. The detail sits in S.I. 2026/1018 on legislation.gov.uk (opens in a new tab), which amends the ISA rules from 1998.

The stated aim is to nudge savers from cash towards shares. So the government has also closed the obvious workarounds. You cannot simply park £20,000 of cash in a stocks and shares ISA instead.

Who keeps the full £20,000 cash limit?

You keep the £20,000 limit if you are 65 or over at the end of the tax year. HMRC's explanatory memorandum applies the £12,000 cap to anyone aged 64 or under at year end. So your age on 5 April decides your limit. Your age on the day you pay in does not matter.

That helps people with a birthday late in the tax year. Say you turn 65 in February 2028. You are 65 at the end of 2027-28. So you can pay £20,000 into a cash ISA from April 2027, while still aged 64.

Still, check the date first. If you turn 65 on or after 6 April 2028, you are 64 at the end of 2027-28. In that case the £12,000 limit applies for that year, and the higher limit opens in 2028-29.

Can you still move a stocks and shares ISA into cash?

Not if you are under 65. From 6 April 2027, you can transfer an investment ISA into a cash ISA only if you are 65 or over at year end. The rule stops people routing money through an investment ISA and then into cash.

For many Americans this matters more than the headline cut. Plenty of US persons opened a stocks and shares ISA before anyone warned them about PFICs. The usual escape route is to sell the funds and move the cash into a cash ISA. That keeps the wrapper for British purposes.

That route stays open until 5 April 2027. After that, an American under 65 can leave the cash in the investment ISA, where interest meets a 22% charge, or withdraw it. So if a clean-up is on your list, do it in 2026-27. Selling a PFIC still has US costs, which our guide to the PFIC problem with ISAs covers.

What happens to cash left inside a stocks and shares ISA?

From 6 April 2027, interest on cash in an investment ISA meets a flat charge at the savings basic rate. The memorandum sets that at 22%. The ISA manager pays it, not you. Also, money market funds can no longer make up the whole of a stocks and shares ISA.

This closes the obvious dodge. Before the change, an investment ISA could be little more than cash. It earned tax-free interest above the cash cap, but now that interest is taxed inside the wrapper. A portfolio of nothing but money market funds no longer qualifies either.

For a US person, the charge raises a fresh question. You report the interest on your American return either way. But we have not seen IRS guidance on whether a charge paid by the manager is a tax that you paid. So treat any credit for it as uncertain.

Why did the cash ISA matter more to Americans?

Because it was the one ISA a US person could hold without PFIC trouble. America ignores the ISA wrapper, so the interest is taxed either way. But a cash ISA holds bank deposits, not shares in a foreign fund. So it avoids Form 8621 and the harsh rules for foreign funds.

A British saver sees the ISA as a tax shelter. You see it differently. For you, a cash ISA is a savings account that HMRC ignores and the IRS taxes in full. That is a fair deal, because at least one government leaves the interest alone.

A stocks and shares ISA is another matter. Most hold British unit trusts, OEICs or ETFs, which the IRS usually treats as PFICs. The paperwork alone can cost more than the tax saved. So for many US persons, the cash ISA was the whole ISA plan.

Is cash ISA interest taxable on your US return?

Yes. The IRS taxes US citizens and green card holders on worldwide income. Nothing in the treaty exempts ISA interest, so every pound of cash ISA interest goes on your US return, converted to dollars. That is true even though HMRC never treats it as income.

The IRS page for US citizens abroad (opens in a new tab) says you are taxed on worldwide income from all sources. ISA interest is no exception. It goes on Schedule B with your other interest. It can also bring the foreign account questions in Part III into play.

Also, the foreign earned income exclusion does not help here. It covers earned income, such as salary. Interest is unearned income, so the exclusion cannot shelter it.

Why can't the foreign tax credit cancel the US tax?

Because there is no British tax to credit. The foreign tax credit only reduces US tax by foreign income tax you actually paid on that income. Cash ISA interest is free of UK tax. So the credit has nothing to work with, and the US tax on it is a real cost.

In practice, many Americans in Britain carry spare credits from tax on their salary. However, those credits sit in the general category. Interest normally falls in the passive category. Credits cannot move between the two, so spare PAYE credits rarely cover ISA interest.

This leads to an odd result. Interest in a taxable account often costs you nothing extra in America. The British tax on it produces a credit. The ISA interest is the interest that actually costs you US tax.

Why does losing £8,000 of cash allowance hurt a US person more?

Because the £8,000 that leaves cash can only go into an investment ISA. For a British saver that is a fine home. For a US person it usually means PFIC funds. So in practice, your usable ISA allowance falls from £20,000 to £12,000 a year.

A British saver under 65 can still shelter £20,000 a year. They simply accept some risk on the last £8,000, while you face a harder choice. You can buy funds and take on PFIC reporting, buy single shares inside the wrapper, or leave the £8,000 unused.

Leaving it unused is often the right call. The wrapper never saved you US tax. So walking away from part of it costs only the British relief. Whether that matters depends on your UK tax rate and your savings allowance.

A worked example: £20,000 of savings before and after the change

The figures below are illustrative. They assume a higher-rate taxpayer aged 40 who saves £20,000 a year at 4%. Their £500 savings allowance is already used on other interest. They pay US tax at 24%, and we use $1.30 to the pound.

1. Before the cash ISA changes 2027: £20,000 in a cash ISA earns £800. UK tax is nil.
2. US tax on that interest: £800 at $1.30 is $1,040, and 24% of $1,040 is $249.60. No credit is available.
3. After the change: £12,000 in the cash ISA earns £480, still free of UK tax. US tax: £480 is $624, and 24% is $149.76.
4. The other £8,000 sits in an ordinary savings account and earns £320. At the 2027-28 higher savings rate of 42%, UK tax is £134.40.
5. US tax on the £320: $416 at 24% is $99.84. The UK tax of £134.40, about $174.72, is larger, so the credit wipes out the US tax on that slice.
6. Total tax after the change: £134.40 in Britain plus $149.76 in America, against $249.60 before. In dollars that is roughly $324 against $250.

So in this example, the change costs about $75 a year. That is modest, but it grows with your savings. The spare credit of about $75 only helps if you have other passive income. A real return must also match the two tax years, which this example ignores.

Will savings interest outside an ISA cost more from April 2027?

Yes. From 6 April 2027, the savings rates rise by two points across the UK. They become 22% basic, 42% higher and 47% additional, and the £5,000 starting rate band is unchanged. The personal savings allowance stays at £1,000 for basic rate and £500 for higher rate taxpayers.

HMRC's technical note on savings and dividend rates (opens in a new tab) confirms those figures. So money pushed out of a cash ISA lands somewhere more expensive. For a British saver, that doubles the pain.

For you, the higher rate is partly offset. British tax on taxable interest now usually exceeds the US tax on it. So the credit removes the American bill on that slice. Our guide to UK savings interest and US tax covers that in more detail.

Where can money above the new cap go?

You have four sensible homes for savings above £12,000. These are taxable savings accounts, Premium Bonds, gilts held directly, and single company shares. Each works in both tax systems without PFIC reporting. The right mix depends on when you need the money and your UK tax rate.

• Taxable savings accounts: simple, with British tax that usually produces a foreign tax credit to offset the US bill.
• Premium Bonds: prizes are free of UK tax but taxable in America. Our guide to Premium Bonds and US tax explains how to report them.
• Gilts bought directly: gains are free of UK capital gains tax, and a low-coupon gilt keeps taxable interest small. See our note on UK gilts and US tax.
• Individual shares: shares in single companies are not funds, so they are generally outside the PFIC rules.
• A workplace pension: still the strongest wrapper for many Americans, because the treaty generally respects it.

Notice what is missing. A British saver leaving cash would usually buy a tracker fund. For you, that is often the worst choice, for the same PFIC reasons as before.

Is a stocks and shares ISA now worth opening?

Only if you fill it with single company shares. A stocks and shares ISA full of British funds is still a PFIC problem for a US person. The cash ISA changes 2027 do not alter that. So the spare £8,000 is not an invitation to buy funds.

Some Americans do hold an ISA of single shares. Those shares are usually not PFICs, and Britain does not tax the gains, though America does. But with no British tax, there is no credit. So the question is whether the British relief is worth the extra US work.

Do you still report ISA accounts to the IRS and FinCEN?

Yes. A cash ISA is a foreign financial account, so it counts towards the $10,000 FBAR threshold across all your foreign accounts. It may also go on Form 8938 if your foreign assets pass the thresholds for people abroad. The ISA wrapper changes none of that.

The IRS comparison of Form 8938 and FBAR rules (opens in a new tab) sets out the thresholds for taxpayers abroad. If you are single, Form 8938 applies above $200,000 at year end or $300,000 at any time. For joint filers, those figures are $400,000 and $600,000.

The FBAR is filed with FinCEN, not the IRS. It is due on 15 April, with an automatic extension to 15 October. If you open new accounts after April 2027, each one goes on the form.

Does the change affect a flexible ISA?

Yes, in a small way. A flexible ISA lets you take cash out and put it back in the same year without using fresh allowance. From April 2027, money you put back into a cash ISA cannot take you over the £12,000 cash limit. So the flexibility now works inside the lower cap.

This matters if your cash ISA is your emergency fund. You can still withdraw and replace within the year. But you cannot use that feature to go past the new limit.

What about a Junior ISA?

The memorandum says the new money market fund rule does not apply to Junior ISAs. The £12,000 cap concerns adult cash ISAs. HMRC's papers do not announce a change to Junior ISA limits. So the change mainly affects your own savings, not your children's accounts.

Even so, a Junior ISA for a US citizen child has the same American issues. Interest in a cash Junior ISA is taxable on the child's US return. A fund-based one is usually a PFIC.

What if you leave Britain?

You can keep an existing ISA after you move abroad, and it keeps its UK tax relief. But you cannot pay into it while you are not UK resident. Crown servants, the armed forces and their spouses are the exception. So the £12,000 limit only matters while you live here.

If you move back to America, the ISA becomes even less useful. America still taxes the interest, and you can no longer add to it. So many people close cash ISAs when they leave. That also shortens the FBAR.

How should you plan before April 2027?

Use the rest of 2026-27 to act while the old rules apply. Check your age position, then fund the cash ISA while the £20,000 limit still applies. Sort out any stocks and shares ISA before transfers to cash close. Then decide where savings above £12,000 will go.

1. Work out your age on 5 April 2028. If you will be 65 or over, the old £20,000 cash limit carries on for you.
2. Fund your cash ISA for 2026-27 by 5 April 2027, using up to £20,000 if you have it.
3. Review any stocks and shares ISA. If it holds funds and you plan to sell, transfer the proceeds to a cash ISA before 6 April 2027.
4. Choose a home for savings above £12,000 a year: taxable accounts, Premium Bonds, gilts or single shares.
5. Update your list of foreign accounts for the FBAR and Form 8938, including any new accounts you open.
6. Check whether British tax on taxable interest now produces foreign tax credits you can use.

Do these steps in order. The transfer window in step three is the only one that closes for good. You can adjust everything else each year.

Common mistakes we expect to see

Most errors will come from treating the change as purely British. These are the ones to avoid.

• Putting the spare £8,000 into a British fund inside a stocks and shares ISA, then missing Form 8621.
• Assuming cash ISA interest stays off the US return because HMRC ignores it.
• Missing the 5 April 2027 deadline to move sold-down funds into a cash ISA while under 65.
• Counting age on the date of the deposit, rather than at the end of the tax year.
• Opening several new savings accounts and leaving some off the FBAR.
• Claiming a foreign tax credit for the 22% charge on cash in an investment ISA without checking it is creditable.

How US UK Tax Accountants helps

We prepare US and UK returns for Americans in Britain, so we see both sides of each savings choice. We can check how the cash ISA changes 2027 affect your plan. We report ISA interest correctly on your US return. And we file your British return through our UK self assessment service.

Perhaps you hold an investment ISA you want to unwind before the window closes. Or you are not sure where your savings should go. Either way, contact us and we will review your position.

This article is general information, not personal tax advice. Rules can change, and your own facts matter, so take advice before you act.

Last reviewed: 12 November 2026.