Ask most people what happens to their cash ISA allowance in eighteen months' time and you'll get a shrug. That's a problem, because the change coming in April 2027 will affect more ordinary savers than almost anything the Treasury has done to household finances this decade. If you keep your emergency fund, house deposit or just a rainy-day cushion in a cash ISA, the rules around how much of it stays tax-free are about to shrink — and the government wants the difference pushed into the stock market instead.
Why Cash ISAs Are Suddenly a Hot Topic Again
The Individual Savings Account has been the default home for UK savings since 1999, and the appeal was always simple: put money in, never pay tax on the interest, no forms, no faff. Chancellor Rachel Reeves confirmed in the Autumn Budget that this simplicity was exactly the problem from the Treasury's point of view. Roughly £300 billion sits in UK cash ISAs, according to HM Treasury's own figures, and ministers have decided that too much of it is earning 4% interest when it could, in their view, be earning more in a stocks and shares ISA and doing more for UK company investment along the way. Whether you agree with that framing or not, the mechanism they've chosen is a hard cap, not a gentle nudge.
What Actually Changes From April 2027
The £12,000 Cap for Under-65s
From the 2027–28 tax year, anyone under 65 will only be able to put £12,000 of new money into a cash ISA each year. The overall £20,000 ISA allowance stays exactly where it is — nothing changes there — but the remaining £8,000 has to go into a stocks and shares ISA, a Lifetime ISA, or an Innovative Finance ISA if you want to keep the tax shelter. Put money into a savings account outside an ISA instead, and HMRC treats the interest as taxable income once you exceed your Personal Savings Allowance (£1,000 for basic-rate taxpayers, £500 for higher-rate).
Why Over-65s Get to Keep the Full £20,000
Savers who are 65 or older on 6 April 2027 are exempt from the new cap and keep the full £20,000 cash ISA allowance, untouched. The Treasury's stated reasoning is that older savers are closer to needing their money and shouldn't be pushed into market risk at that stage of life. Fair enough as a principle — but it does mean two people with identical savings habits, one 64 and one 65, will be treated completely differently from the same tax year onward.
Where the Rest of Your Allowance Has to Go
This is the part that trips people up. The £8,000 difference doesn't vanish and it doesn't automatically move anywhere — you have to actively open and fund a stocks and shares ISA, a Lifetime ISA (capped at £4,000 a year with a 25% government bonus, useful if you're under 40 and saving for a first home), or an Innovative Finance ISA for peer-to-peer lending. Miss the deadline in any given tax year and you simply lose that portion of the allowance; it doesn't roll over. Providers like Hargreaves Lansdown, AJ Bell, Vanguard and Nutmeg all offer stocks and shares ISAs with low-cost index tracker options, and several — Moneybox among them — now let you split contributions between a cash and stocks ISA inside a single app.
And if you do nothing at all? The £8,000 simply goes unused — it isn't held over, it isn't added to next year's allowance, and there's no grace period after the tax year closes on 5 April. Say you're 42, earning a decent salary, and you've been putting the full £20,000 into a Nationwide cash ISA every year without thinking twice about it. From April 2027 you'd need to actively open a second account with a second provider, transfer the excess yourself, and decide on an investment strategy you may never have needed before — all inside the same twelve months, or lose the tax shelter on that portion for good.
Is Your Cash Actually Safe? FSCS Protection Explained
None of this changes how your deposits are protected, which is worth separating out clearly because the two issues get muddled constantly online. The Financial Services Compensation Scheme protects up to £85,000 per person, per banking licence, if a bank, building society or credit union fails. That's the number that matters, not the ISA wrapper.
The £85,000 Limit — and Where It Trips People Up
Here's the catch that catches out even savers who think they understand this: several well-known UK brands share a single banking licence, so your money isn't as spread out as the logos suggest. Halifax and Bank of Scotland sit under the same licence as part of Lloyds Banking Group. HSBC and First Direct share one. If you hold £60,000 with Halifax and £40,000 with Bank of Scotland thinking you've diversified your protection, you haven't — you're £15,000 over the limit and exposed on the excess. Check the FSCS's own licence lookup tool before you assume you're covered, because the marketing names on the app icon tell you nothing about the underlying licence.
The Real Alternatives: Easy-Access Accounts Outside an ISA
For a lot of people, especially those with less than £20,000 in savings altogether, the ISA cap change barely matters in practice — the Personal Savings Allowance already covers most of what a typical easy-access account pays out in interest each year. If your total savings sit below roughly £25,000, a good non-ISA easy-access account and a decent PSA will probably cover you without an ISA at all.
Comparing Monzo, Starling, Chase UK and NS&I
Chase UK has built a loyal following on its saver account paying a competitive variable rate with no minimum balance, though the headline rate typically includes a temporary bonus that drops after the first year — read the small print before you assume it's permanent. Starling's easy-access saver pays interest daily and integrates neatly with its main current account, which suits people who move money between pots often. Monzo offers similar flexibility through its instant access savings pots, backed by partner banks rather than Monzo itself holding the FSCS protection directly — worth knowing, since the protection sits with the underlying bank, not the app you're tapping. NS&I remains the outlier: it's backed by HM Treasury rather than the FSCS scheme, meaning 100% of your deposit is protected regardless of size, though its rates have lagged the best challenger-bank offers for much of the past two years.
None of these four is objectively “the best” — it depends entirely on how you use money day to day, whether you want everything in one app, and how much you're actually saving. If you're the kind of saver who checks a balance three times a day, Starling or Monzo will suit you better than a bank you only log into once a quarter. If you want to forget the account exists and trust the guarantee behind it more than the interest rate, NS&I is the calmer choice, even though the numbers on paper look less exciting.
Should You Rush Into a Stocks and Shares ISA?
Not necessarily, and definitely not just because the Treasury would prefer you did. A stocks and shares ISA makes sense for money you won't need for at least five years, ideally longer, because the whole point of accepting market risk is giving it time to smooth out. Money you might need for a deposit next year, a car repair, or genuine emergencies has no business sitting in equities regardless of what tax wrapper surrounds it.
Choose a low-cost global index tracker if you're going down this route — funds tracking the FTSE All-World or S&P 500 through providers like Vanguard or Fidelity typically charge under 0.25% a year, which matters enormously over a couple of decades of compounding. Avoid actively managed funds charging 1%+ unless you have a specific reason to believe that particular manager will consistently beat the index, because most don't, over most periods, after fees.
My Take: Who Actually Benefits From This Reform
Here's my honest view after going through the Treasury's own consultation documents: this reform helps confident, engaged savers who were already planning to invest eventually and just needed a shove. It does very little for the person with £8,000 in a Halifax cash ISA who has no interest in market risk and never asked for this choice to be made for them. Calling it a simplification, as some coverage has, is generous — it adds a second account, a second provider relationship, and a second set of terms to track for anyone who wants to keep their full £20,000 sheltered from tax.
If you're under 65 and currently maxing out a cash ISA, the sensible move before April 2027 arrives is to work out how much of that £20,000 you genuinely need in cash versus how much you were only keeping there out of habit. For the portion you won't touch for five years or more, a stocks and shares ISA through a low-cost provider is a reasonable place to put it — but open the account on your own timeline, once you understand what you're buying, not in a scramble the week the cap takes effect.