From April 2027, a new 22% tax charge will be levied on interest earned from cash held within Stocks & Shares Individual Savings Accounts (ISAs). This marks a notable shift in the landscape for UK savers, particularly those who have historically used their investment wrappers to hold significant uninvested cash balances.
What Changed and By How Much?
The most significant alteration, stemming from announcements in the Autumn Budget 2025, is the introduction of a 22% tax on interest generated by cash held within a Stocks & Shares ISA. Previously, all gains and income within an ISA wrapper, including interest on cash, were entirely tax-free. This new charge specifically targets the uninvested cash component, not the returns from actual stock, fund, or bond investments.
The overall annual ISA allowance, which currently stands at £20,000, will remain unchanged. This means you can still contribute up to £20,000 across your various ISA types each tax year, but how that money behaves once inside a Stocks & Shares ISA, if left as cash, is now subject to new scrutiny.
Why the Change?
The Treasury's rationale is clear: to encourage greater investment in equities and support UK economic growth. For some time, there has been a perception that a segment of savers used Stocks & Shares ISAs as a de facto high-interest cash account, rather than for their intended purpose of long-term investment in growth assets. This new tax is designed to nudge savers towards deploying their capital into the market, or into a dedicated Cash ISA.
Scenario: If you have X this means Y
Consider a saver, Sarah, who has £5,000 in uninvested cash within her Stocks & Shares ISA, earning an annual interest rate of 4%. Currently, this £200 in annual interest is entirely tax-free.
From April 2027, that same £200 interest will be subject to the new 22% charge. This means £44 (£200 x 0.22) will be deducted in tax, leaving Sarah with £156 in net interest. While not a catastrophic sum, it represents a direct reduction in her tax-free earnings within a product designed for tax efficiency.
What this means for you
If you currently hold substantial uninvested cash within a Stocks & Shares ISA, you will need to review your strategy before April 2027. The 22% tax means that simply leaving cash in this wrapper will no longer offer the same tax-free benefits on interest as it once did. You should consider whether this cash would be better placed in a dedicated Cash ISA, or indeed, invested in line with the Stocks & Shares ISA's primary purpose.
Step-by-step what to do right now
- Review your holdings: Check your Stocks & Shares ISA statements to identify any uninvested cash balances.
- Assess your goals: Determine if this cash is genuinely awaiting investment, or if it's being held for shorter-term savings.
- Consider alternatives: If the cash is for savings, explore moving it to a Cash ISA, where interest remains entirely tax-free up to your annual allowance. For first-time buyers under 40, a Lifetime ISA offers a 25% government bonus on contributions up to £4,000 per year, which can be a significant boost.
- Invest if appropriate: If the cash is intended for long-term growth, consider investing it within your Stocks & Shares ISA, aligning with the government's stated aim.
Remember, interest earned on standard savings accounts outside of an ISA may be subject to tax above your Personal Savings Allowance (£1,000 for basic rate taxpayers, £500 for higher rate taxpayers).
When Effective
These new rules will come into effect from April 2027. This provides savers with a reasonable window to review their arrangements and make any necessary adjustments.
Where to Get Help
For personalised guidance on your specific financial situation, it is always advisable to consult an independent financial adviser. They can help you navigate the complexities of ISA rules and ensure your savings and investments are structured efficiently.
The Other Side: Government's Intent
While some may view this as an erosion of the ISA's tax-free status, the government maintains that the change is a targeted measure. The aim is not to penalise savers but to re-align the Stocks & Shares ISA with its original purpose: encouraging long-term investment in the capital markets. By doing so, the Treasury hopes to channel more funds into productive assets that can contribute to broader UK economic growth, rather than simply sitting as cash.
This is not financial advice. Seek independent financial guidance. Interest on standard accounts may be subject to tax above your Personal Savings Allowance.
Sources
- AI-Researched Primary Sources — New ISA Rules: Tax Implications for UK Savers from April 2027
- Money Saving Expert — Cash held in stocks and shares ISAs to be hit with 22% charge on interest from April 2027
- The Guardian — HMRC announces 22% tax on cash interest held in stocks and shares Isas
- Morningstar — ISA Tax Changes Explained: What Savers Need to Know
- Daily Business — Reeves hammers Isa savers with new tax charge