The £12,000 cash ISA cap from April 2027: what changes and what it means

For twenty-five years the ISA allowance came with one number attached to it. From April 2027 it comes with two, and the gap between them is the point.

What is changing

From 6 April 2027, the amount that can be paid into a cash ISA each tax year falls to £12,000 for savers under 65. The overall ISA allowance is unchanged at £20,000. The remaining £8,000 can still be sheltered from tax — but only in a stocks and shares ISA, an innovative finance ISA or a Lifetime ISA.

Savers aged 65 and over are exempt and can continue to use the full £20,000 in cash. The Junior ISA allowance is unaffected at £9,000.

The change was announced at the Autumn Budget in November 2025. It is the first reduction in a headline adult ISA limit since ISAs launched in 1999.

Who it affects

Less broadly than the headlines suggest, and more sharply than the averages imply.

Most ISA savers do not use the full allowance in any given year, so for them the cap changes nothing in practice. Industry research published around the Budget put the proportion of ISA holders saving or investing the full £20,000 at roughly one in six.

The people it does affect fall into two groups. The first is anyone under 65 who genuinely uses the full allowance in cash — often people saving for a house deposit, a known near-term cost, or simply savers who prefer certainty. From 2027/28 they face a decision they have not had to make before: invest £8,000, or save it outside a tax wrapper.

The second group is larger and quieter: people who would never have used the full allowance anyway, but who will now encounter a prompt to think about investing where none existed before. That, in policy terms, is the intended effect.

Why the government did it

The stated purpose is to shift some of the money sitting in UK cash accounts toward investment, and toward UK equities in particular. The reasoning runs from a well-documented starting point: the FCA's own research identifies millions of UK adults holding substantial balances entirely in cash, and only a small minority taking regulated advice about it.

Whether a cap achieves that is contested. Building societies argued during consultation that it would deter saving without necessarily creating investors. The counter-argument is that the £8,000 gap is a nudge rather than a compulsion, and that the alternative — leaving the choice entirely unprompted — has produced the current position.

Both positions are worth understanding, because the change is a policy bet rather than a settled fact.

The second change most people missed

The cash ISA cap does not arrive alone. From April 2027, the income tax charged on savings interest earned outside an ISA is also rising by two percentage points across the bands, to 22%, 42% and 47%.

That matters because it changes the maths of the obvious workaround. Someone who decides simply to hold the extra £8,000 in an ordinary savings account rather than invest it will, from the same month, pay more tax on any interest above their personal savings allowance than they would today.

The two measures pull in the same direction: sheltered cash becomes scarcer, and unsheltered cash becomes more expensive.

What 2026/27 means

The current tax year runs to 5 April 2027, and the cap applies to contributions made from 6 April 2027 onward. In practical terms:

• 2026/27 is the last full tax year in which an under-65 can pay the entire £20,000 into a cash ISA.
• Money already in a cash ISA is untouched. Existing balances, including those built up in earlier years, keep their tax-free status indefinitely.
• Transfers are not contributions. Moving an existing cash ISA between providers does not use allowance, before or after the change.

Note also that the measures were announced at Budget and remain subject to the legislative process; final detail, including new rules on transfers between ISA types, is still being confirmed.

The options

There is no single correct response, and what follows is a description of the choices rather than a recommendation.

Use the current year fully. Anyone who intends to hold a large cash ISA balance and is comfortable doing so has until 5 April 2027 to place up to £20,000 under the existing rules.

Split from 2027/28. Pay £12,000 into cash and direct £8,000 into a stocks and shares ISA. This is the outcome the policy is designed to produce, and it carries investment risk that cash does not — capital can fall as well as rise.

Contribute less. The cap limits what can go into a cash ISA; it does not require anyone to invest the difference. Paying in £12,000 and stopping there is a perfectly valid choice.

Save the balance outside an ISA. Possible, and increasingly costly from April 2027 given the higher savings tax rates, though the personal savings allowance still shelters a first slice of interest for many people.

Consider pensions separately. Pension contributions have their own allowances and their own tax treatment, and are not affected by this change.

What has not changed

The overall £20,000 allowance. The tax-free treatment of everything inside an ISA. The rule that allowances do not carry forward — unused allowance still disappears at midnight on 5 April, every year, cap or no cap.

That last point is the one that costs people money regardless of the policy. Knowing how much of your allowance you have actually used, across every provider you hold an ISA with, remains something no single institution can tell you — and it becomes more consequential once the allowance is split into two limits rather than one.

Related: The £20,000 ISA allowance: how it works, and what actually counts

Sources

• HM Treasury — Budget 2025, accessed August 2026.
• UK Parliament, Treasury Committee — Cash ISA: Government Response, accessed August 2026.
• HM Revenue & Customs — Individual Savings Accounts (ISAs), accessed August 2026.
• HM Revenue & Customs — Annual savings statistics, accessed August 2026.
• Financial Conduct Authority — Financial Lives 2024 survey, accessed August 2026.

Last reviewed: 2 August 2026 · Figures reflect the 2026/27 UK tax year.

This article is general educational information about UK tax and investing rules. It is not personal advice or a recommendation, and it does not take account of your circumstances. Tax treatment depends on individual circumstances and may change. Figures reflect our understanding of the rules for the 2026/27 tax year at the date of publication. If you are unsure, consider speaking to an adviser authorised by the FCA.