How to beat the Cash ISA allowance cut as half of savers risk higher tax bill

Millions of UK savers could end up paying more tax on their savings after the Government made changes to how much you can stash away tax-free in a Cash ISA.

While the overall £20,000 annual ISA allowance remains in place, the November 2025 Budget introduced a new lower cap on how much of that can sit in cash – a move designed to nudge savers towards investing on the stock market instead.

But with interest rates still relatively high and many households preferring the certainty of cash, the change risks landing ordinary savers with an unexpected tax bill.

Industry estimates suggest around half of Cash ISA savers could be affected, particularly those with larger emergency funds or long-term cash savings.

So what exactly has changed – and how can you protect your money?

ISA rules for 2027/28

Under the new rules, the amount you can put into a Cash ISA each tax year has been reduced, even though the overall ISA allowance is unchanged.

The full allowance remains at £20,000 but only a maximum of £12,000 can be put into a Cash ISA each year. Anything above that must go into a Stocks and Shares ISA to still keep the tax-free benefits an ISA brings.

Why this could be a problem for savers

Any savers who previously kept most – or all – of their £20,000 allowance in cash will now need to rethink how they save.

Research by investment platform AJ Bell suggests more than half (51%) of Cash ISA savers will simply put their money into a taxable savings account, rather than Stocks and Shares ISAs which are considered a more long term investment due to the fluctuating markets.

But that could cost savers hundreds of pounds a year in extra tax.

Any interest made in accounts not in an ISA wrapper is subject to tax once you exceed your personal savings allowance, which is:

With many easy-access savings accounts now paying 4% or more, it doesn’t take a huge balance to tip people over those limits.

Read more: Cash ISAs vs Stocks & Shares ISAs: Which is best?

What £8,000 grows to and how much tax you could pay outside an ISA

At first glance, putting £8,000 a year into a cash savings account doesn’t look like the sort of thing that should trigger a tax bill. We’ve calculated what a modest 2% interest rate would give savers, and the returns in the early years are small and easy to ignore.

In year one, the account earns just £160 in interest — comfortably within the personal savings allowance for both basic- and higher-rate taxpayers.

But the table below shows why looking at savings year by year can be misleading.

This example assumes £8,000 is added to the same savings account every year, with the interest left untouched so it compounds. Over time, the pot grows steadily, and so does the amount of interest it generates each year.

By year four, a higher-rate taxpayer is already paying tax on their savings interest. By year six, even a basic-rate taxpayer starts to cross the £1,000 allowance, triggering a tax bill for the first time.

By the end of year 10, the account has theoretically grown to around £89,000, generating £1,752 in interest a year. On its own, that annual tax bill still doesn’t look dramatic — but over time it quietly adds up. Across the decade, a basic-rate taxpayer would pay nearly £400 in tax, while higher- and additional-rate taxpayers could lose thousands of pounds to the taxman.

We’ve used a 2% interest rate for this example to reflect a more realistic long-term average. While the best easy-access accounts are currently paying around 4.5%, rates have been far lower in the past - with the Bank of England base rate dropping to just 0.1% during Covid. Over a 10-year period, savings rates are likely to fluctuate, so we’ve used 2% to represent a sensible middle ground that broadly aligns with the Bank of England’s long-term inflation target. A different interest rate on your account would result in different amounts of earned interest and taxes. Use these figures as an illustrative example only.

How to beat the Cash ISA allowance cut

With a bit of planning, there are still plenty of ways to keep more of your savings tax-free.

1. Use your full ISA allowance – but split it smartly

You don’t have to choose between cash or investing.

Many savers can opt for a mix of Cash ISAs and Stocks & Shares ISAs, for example, using cash for short-term needs or emergencies and investments for longer-term goals.

You still get tax-free growth – just in different accounts.

Historically, investing in the stock market has delivered higher average returns than cash. Long-term global stock market returns have averaged around 5–7% a year after inflation over long periods - significantly more than most savings accounts manage outside periods of unusually high interest rates. That said, historical returns are no guarantee of future returns, and you can lose money when investing in the stock market.

And the stock market can be volatile. For this reason, it's generally considered to be safer if money invested in the stock market is money invested for the longer term. Investing money you might need in the short term adds a layer of risk, in case of a market downturn.

But if the market continues to outperform cash then the difference can add up, particularly once tax on savings interest starts to creep in.

Crucially, any growth or income inside a Stocks & Shares ISA is tax-free, just like a Cash ISA.

Investing doesn’t have to mean picking individual shares. Many people choose diversified funds that spread money across hundreds or thousands of companies linked to how much risk you say you want to take.

The key is time. Cash suits short-term certainty. Investing typically tends to suit longer-term goals, all while keeping returns safely out of the taxman’s reach.

Read more: Cash ISAs vs Stocks & Shares ISAs: Which is best?

2. Don’t leave old ISAs on autopilot

Older Cash ISAs often pay poor rates, so review what you already have to see if you’re earning a competitive rate or if part of that money be better placed elsewhere.

You can usually transfer ISAs without losing tax protection, as long as you follow the proper transfer process – including transferring it, not withdrawing to put it somewhere else.

3. Make the most of your partner’s allowances

Because savings allowances are applied per person, not per household, couples could reduce tax by making sure both partners use their own ISA and savings allowances.

In practice, this can mean spreading savings more evenly between two people, rather than allowing one partner, such as the higher earner - to hold everything in their own name and pay unnecessary tax on the interest.

However, it’s important to be clear that money saved in your partner’s name legally belongs to them. Using a partner’s allowances can make sense where finances are already shared, but it relies on trust and isn’t right for everyone.

There’s also a separate, often-overlooked rule that applies if a spouse or civil partner dies. In that situation, the surviving partner is entitled to an Additional Permitted Subscription (APS) — an extra ISA allowance equal to the value of the deceased partner’s ISA at the time of death. This allows the money to keep its tax-free status, on top of the survivor’s own annual ISA allowance.

**We explain more about APS here: Little-known rule that could see your ISA allowance skyrocket: 'Really valuable’

4. Consider Premium Bonds for tax-free returns

While not guaranteed, Premium Bond prizes are tax-free and don’t count towards ISA limits.

They won’t suit everyone, but for higher-rate taxpayers already maxing out ISAs, they can potentially be a useful overflow option.

5. Check whether you’re paying tax on savings without realising

Tax on savings interest is usually collected automatically, which means many people don’t realise they’re paying it at all.

If you earn more interest than your personal savings allowance allows, HMRC often collects the tax by changing your tax code, rather than sending you a bill. That can reduce your take-home pay or pension slightly each month, without any obvious explanation.

If your tax code has changed recently it’s worth checking:

Catching it early gives you time to move money into tax-free options, such as ISAs, rather than losing interest quietly through your payslip later on.

Disclaimer: ISA Tax treatment depends on your individual circumstances and may be subject to change in the future. This article does not constitute any form of tax or investing advice. Readers are responsible for carrying out their own due diligence and for obtaining professional advice before making any investment decisions.

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