ISA Reform 2027: Closing the Cash ISA Loophole

When the Government announced changes to the ISA regime, much of the attention focused on the future of the Cash ISA allowance.

However, one of the more significant developments has received far less publicity: new rules designed to stop Stocks & Shares ISAs being used as a substitute for Cash ISAs.

From April 2027, HMRC will introduce a series of anti-circumvention measures aimed at ensuring each type of ISA is used for its intended purpose. While these reforms are unlikely to affect most long-term investors, anyone who regularly holds large cash balances within a Stocks & Shares ISA should understand what is changing and whether they need to review their investment strategy.

Why are the rules changing?

ISAs have always been designed with different objectives in mind. A Cash ISA provides a tax-efficient home for savings, while a Stocks & Shares ISA is intended for investing over the longer term.

In recent years, however, some investors have used Stocks & Shares ISAs to hold substantial amounts of cash or cash-like investments, effectively gaining the flexibility of an investment ISA while using it much like a Cash ISA. HMRC's view is that this was never the intention of the legislation, and the new rules are designed to close that loophole.

What is changing?

From April 2027, several new measures will come into force.

A 22% charge on cash interest within non-Cash ISAs

Interest, or equivalent returns, earned on cash held within a non-Cash ISA will become subject to a 22% charge. The aim is to discourage investors from leaving significant cash balances sitting uninvested inside Stocks & Shares ISAs for prolonged periods.

Cash-only portfolios will no longer qualify

HMRC is also introducing restrictions on portfolios made up entirely of cash-like investments. For the purposes of the new rules, Money Market Funds are treated as cash-like assets.

Importantly, this does not mean Money Market Funds can no longer be held within a Stocks & Shares ISA. They will remain a perfectly acceptable component of a diversified investment portfolio. What changes is that they can no longer be used to create an ISA invested entirely in cash-equivalent assets.

Changes to ISA transfers

The reforms also affect transfers between ISA wrappers.

At present, some investors subscribe to a Stocks & Shares ISA before transferring those funds into a Cash ISA. HMRC considers this another way the Cash ISA rules can be circumvented.

From April 2027:

• Transfers from non-Cash ISAs into Cash ISAs will no longer be permitted.
• Transfers from Cash ISAs into non-Cash ISAs will continue to be allowed.

This means investors will still be free to move from cash into investments, but not the other way around.

What does this mean for investors?

For many investors, the answer is very little.

If your Stocks & Shares ISA is invested as intended and any cash is held only temporarily while awaiting investment or portfolio rebalancing, these changes are unlikely to have any meaningful impact.

However, if you've deliberately used a Stocks & Shares ISA to hold significant cash balances or relied heavily on Money Market Funds as a cash alternative, now is a good time to review your arrangements before the new rules take effect.

The reforms don't fundamentally change the role of ISAs. Instead, they reinforce the distinction between saving and investing, ensuring each type of ISA continues to fulfil the purpose for which it was created. As with any tax changes, reviewing your plans with a Financial Planner can help ensure your strategy remains aligned with both your financial objectives and the latest HMRC rules.