
In the intricate landscape of UK savings taxation, the humble ISA has long been a rare pocket of simplicity: pay in, and your returns grow free of tax. That reputation is about to be tested. As part of the Budget 2025 ISA reforms, HMRC has confirmed a new 22% charge on interest earned on cash held inside non-Cash ISAs, alongside a package of anti-circumvention rules. As accountants in Surrey serving clients across the UK, we are already fielding questions from investors, and here is what you need to know.
What Is Changing — and Why
From 6 April 2027, the annual Cash ISA allowance falls from £20,000 to £12,000 for savers under the age of 65, while those aged 65 and over keep the full £20,000 cash limit. The overall ISA allowance remains £20,000 across all ISA types. The government’s aim is to nudge more people towards Stocks & Shares ISAs and build a stronger retail investment culture.
The obvious workaround would be to open a Stocks & Shares ISA and simply hold cash in it — sidestepping the lower Cash ISA limit entirely. To close that door, HMRC has introduced targeted anti-circumvention rules.
The 22% Charge on Non-Cash ISA Interest
The headline measure is a 22% charge on interest (or the equivalent “alternative finance return”) paid on cash holdings within Stocks & Shares ISAs and Innovative Finance ISAs — the “non-Cash” ISAs. Crucially, this charge applies universally: it does not matter how old you are, which income tax band you fall into, or even whether you are a taxpayer at all. Interest on genuinely invested holdings is unaffected; it is idle cash sitting in an investment ISA that is targeted.
Two Further Anti-Circumvention Rules
The 22% charge does not stand alone. The confirmed rules also prevent transfers from non-Cash ISAs into Cash ISAs for savers under 65, and prevent holding 100% Money Market Funds within a non-Cash ISA — another route through which cash-like returns could otherwise be sheltered. Together, these measures are designed to keep the reduced Cash ISA limit meaningful. HMRC has said further operational detail will follow in its next Tax Free Savings newsletter.
What It Means for Savers and Investors
For most people who use their Stocks & Shares ISA to actually invest, the practical impact is limited. The change bites for those who park significant sums of cash inside an investment ISA — whether waiting to invest, de-risking, or using it as a de facto savings account. From April 2027, that strategy carries a 22% cost on the interest earned. Reviewing where your cash actually sits, and whether a Cash ISA, a General Investment Account or your reduced Cash ISA allowance is the better home, will matter more than ever.
How TaxDigit Can Help
These reforms sit at the intersection of savings, investment and tax planning — exactly where careful advice pays off. Our Guildford-based team helps clients structure their allowances efficiently ahead of the 2027 changes, and our personal tax specialists can review how the new rules interact with your wider position. For high-net-worth individuals and business owners, our tax advisory and planning service builds ISA strategy into a broader, forward-looking plan. You can read the government’s own confirmation in the Tax update 2026 policy paper.
Plan Ahead With TaxDigit
The 22% charge does not take effect until 6 April 2027 — which means there is time to plan, but not time to ignore it. As premier accountants in Surrey serving clients across the UK, TaxDigit will help you make the most of your allowances before the rules change. Call 01483 230 777, email info@taxdigit.co.uk, or visit our contact page for bespoke advice.
