From April 6, 2027, a significant shift in ISA regulations will see a 22% flat-rate charge levied on any interest earned from cash held within Stocks and Shares ISAs and Innovative Finance ISAs. This isn't merely a tweak; it's a clear signal from the Treasury, designed to reshape how Britons utilise their tax-efficient savings wrappers.
The move, confirmed by HMRC, is part of a package of "anti-circumvention" rules. The government's stated aim is to prevent savers from using non-Cash ISAs as a tax-free haven for substantial cash holdings, particularly as the annual Cash ISA allowance for those under 65 is set to be reduced from £20,000 to £12,000 on the same date. For individuals aged 65 and over, the full £20,000 Cash ISA allowance will remain.
What Changed and By How Much?
- The Charge: A flat 22% charge will apply to interest or "alternative finance return" on cash in Stocks and Shares ISAs and Innovative Finance ISAs. This applies universally, regardless of your income tax bracket, even for non-taxpayers.
- Cash ISA Limit: For those under 65, the annual Cash ISA allowance drops from £20,000 to £12,000.
- Overall ISA Allowance: This remains at £20,000. You can still subscribe up to this amount across various ISA types, but the allocation to cash within a Cash ISA is now capped for most.
- Non-Cash ISA Limits: The annual limit for Stocks and Shares ISAs and Innovative Finance ISAs remains at £20,000. The change is specifically about the cash held within them.
- Transfer Restrictions: From April 2027, transfers from non-Cash ISAs into Cash ISAs will no longer be permitted for individuals under 65. Transfers from Cash ISAs into Stocks and Shares ISAs will still be allowed.
HMRC's factsheet from June 23, 2026, explicitly states the intent: "In order to protect the integrity of the new cash ISA limit and ensure the reforms achieve their intended aim of encouraging retail investment so savers get more from their investments/savings, the following rules will be introduced to prevent the following: subscribe up to £20,000 cash in a non Cash ISA and leave it there long-term earning tax-free interest."
Who is Affected?
This change primarily impacts individuals who have been using their Stocks and Shares ISA or Innovative Finance ISA to hold significant amounts of cash, perhaps while waiting for investment opportunities or simply seeking a tax-free wrapper for high-interest savings. Historically, many have done this, particularly when Cash ISA rates were less competitive or when they had already maxed out their Cash ISA allowance.
Consider this: in the 2023-24 tax year, approximately 15 million adult ISA accounts were opened. Of these, nearly 10 million subscribed to Cash ISAs, while just over 4 million opted for Stocks and Shares ISAs. The government's move appears to be a direct response to the popularity of cash savings, even within investment-focused wrappers.
Scenario: If you have £10,000 in cash in a Stocks and Shares ISA
Let's say you currently hold £10,000 in cash within your Stocks and Shares ISA, earning a respectable 4% interest per annum. Under the current rules, that £400 interest would be entirely tax-free. From April 6, 2027, however, that £400 interest would be subject to the 22% charge, meaning £88 would be deducted, leaving you with £312. This applies irrespective of whether you pay basic, higher, or additional rate income tax, or indeed, no tax at all.
For comparison, if this cash were in a standard savings account, the interest would be taxable above your Personal Savings Allowance (PSA) – £1,000 for basic rate taxpayers, £500 for higher rate. For additional rate taxpayers, there is no PSA. A Cash ISA, even with the reduced allowance, would still offer entirely tax-free interest up to the new £12,000 limit (or £20,000 for those 65+).
What this means for you
If you currently hold cash within a Stocks and Shares ISA or Innovative Finance ISA, it's time to review your strategy. The 22% charge makes holding cash in these wrappers significantly less appealing for its interest-earning potential. Consider whether that cash is genuinely earmarked for investment, or if it would be better placed in a dedicated Cash ISA – remembering the new £12,000 limit for under 65s – or even a Lifetime ISA if you're a first-time buyer saving for a home, benefiting from the 25% government bonus on contributions up to £4,000 per year.
The Other Side: Exemptions and Intent
Not all cash-like assets will fall under the 22% charge. Money Market Funds (MMFs) will not be subject to the charge, provided they do not constitute 100% of the investments within a non-Cash ISA account. HMRC will require ISA managers to report the market value of MMFs. Similarly, short-dated gilts will not be classified as 'cash-like assets' for the purpose of this charge. This suggests the government is targeting readily accessible, uninvested cash, rather than certain low-risk investment vehicles.
The government's broader strategy, as stated by GOV.UK, is to "develop a retail investment culture." The 22% charge, therefore, can be seen as a rather blunt instrument to encourage a more adventurous spirit among savers, nudging them towards actual investments rather than using investment wrappers as glorified, tax-free cash accounts.
Step-by-step what to do right now
- Assess your holdings: Check your Stocks and Shares ISA or Innovative Finance ISA for any significant cash balances.
- Understand the limits: Familiarise yourself with the new £12,000 Cash ISA allowance if you're under 65, effective from April 2027.
- Consider your options: If your cash is genuinely for investment, ensure it is invested. If it's simply savings, explore moving it to a Cash ISA (before the transfer restrictions apply from non-Cash ISAs to Cash ISAs for under 65s) or a Lifetime ISA if appropriate.
- Review your Personal Savings Allowance: Remember that interest on standard savings accounts is taxable above your PSA. For large sums, ISAs remain the most tax-efficient option.
When Effective
The new rules, including the 22% charge and the reduced Cash ISA allowance for under 65s, will come into force from April 6, 2027. HMRC has indicated that a technical consultation with industry on draft legislation will begin shortly, with regulations laid in the autumn.
Where to get help
For personalised advice on your specific financial situation and how these changes might impact your savings and investment strategy, it is always recommended to seek guidance from an independent financial adviser.
Sources
- HMRC Factsheet (June 23, 2026) — details on the 22% charge, Cash ISA limit reduction, transfer restrictions, and purpose of the change.
- GOV.UK (June 23, 2026) — confirmation of anti-circumvention rules and government's wider strategy.
- HMRC (as reported by The Guardian, June 24, 2026) — timeline for consultation and regulations.
- Statistics on ISA Subscriptions (2023-24) — figures on ISA account uptake.
This is not financial advice. Seek independent financial guidance. Interest on standard accounts may be subject to tax above your Personal Savings Allowance.