Rachel Reeves’ ISA reforms are meant to solve a real policy problem in the UK: too much household wealth sitting in cash, and too little flowing into long-term investment. The controversial part is the proposed 22% charge on interest earned from uninvested cash inside a Stocks and Shares ISA from April 2027. On paper, it nudges savers towards risk assets. In practice, several investment and tax specialists argue it may make the ISA system more confusing, less flexible and less trusted.

According to GOV.UK, the ISA allowance is currently 20,000 GBP per tax year across eligible ISA types, including Cash ISAs and Stocks and Shares ISAs (GOV.UK, 2026). The reported reforms would reduce the Cash ISA limit to 12,000 GBP for under-65s from the 2027-28 tax year, while keeping the broader ISA allowance at 20,000 GBP. The 22% charge is designed to stop savers from putting money into a Stocks and Shares ISA and simply leaving it in cash.

1. The reform makes a simple UK product harder to understand

The first criticism is that ISAs work because they are easy to explain: put money in, stay within the annual allowance, and returns are sheltered from tax. Once some interest inside an ISA becomes taxable, that clean message becomes harder to defend.

Rachel Vahey, head of public policy at AJ Bell, told The Guardian that the reforms add tax charges, age-related allowances and reduced flexibility, all of which may discourage would-be investors rather than encourage them (The Guardian, 2026).

That matters because new investors often start cautiously. A person moving from a Cash ISA to a Stocks and Shares ISA may not invest the full amount on day one. They may drip-feed into funds, wait while choosing a platform, or hold cash during a transfer. If that behaviour suddenly creates a tax charge inside an account they thought was tax-free, the lesson may not be “invest more”. It may be “avoid the complicated account”.

The risk is not only technical complexity. It is a trust problem. ISAs have been sold to the public for years as a simple tax shelter. If a reform makes the words “tax-free ISA” feel conditional, savers may become more reluctant to use the wrapper at all.

2. Cash is part of normal investing, not always a loophole

The second criticism is that the rule treats cash as suspicious, even when it is used sensibly. Cash inside a Stocks and Shares ISA can be a short-term parking place before buying investments. It can also build up after dividends, fund sales, transfers, portfolio rebalancing or account administration.

Claire Trott, head of advice at St James’s Place, told The Guardian that holding cash or cash-like assets can be part of a normal investment journey, including while switching investments or waiting for money to be reinvested (The Guardian, 2026).

That is the practical weakness in the policy. It tries to catch people using a Stocks and Shares ISA as a disguised savings account, but it may also catch ordinary admin cash. Investors do not always hold cash because they are avoiding risk forever. Sometimes they are managing timing, platform transfers, income payments or a market entry plan.

A flat charge may not distinguish well between those behaviours. Someone deliberately using a Stocks and Shares ISA as a cash account is different from someone who has sold a fund and is waiting a few days to reinvest. A policy that does not make that distinction could feel blunt to ordinary investors.

3. It may push cautious savers away from investing

The third criticism is behavioural. The government wants more people to invest, but people who have never invested before do not usually move from cash to shares because of a tax penalty. They move when they understand the risks, have an emergency fund, know their time horizon, and trust the wrapper they are using.

MoneySavingExpert’s Stocks and Shares ISA guidance explains that investing is for money that can usually be left for the longer term, because investments can rise and fall in value (MoneySavingExpert, 2026). That point is central. For money needed within the next few years, cash can be appropriate. For longer-term money, diversified investments may offer better potential returns, but only if the saver can tolerate market falls.

Read also: Will ISA Investors in the UK Pay 22pc Tax on Cash Interest?

Rachael Griffin, a tax and financial planning expert at Quilter, has argued that the ambition to encourage investing is reasonable, but the proposals risk making the ISA system feel more complicated at the point cautious savers are being asked to take their first steps (The Guardian, 2026).

That is why the tax may not work as intended. A confident investor can adapt. A nervous first-time investor may simply stay in ordinary savings, use only a Cash ISA up to the lower limit, or delay making any decision. The policy may change account behaviour without creating genuine investment confidence.

4. The personal savings tax picture is already complicated

The fourth criticism is that the wider savings tax system is already hard enough for ordinary households. Cash ISA decisions depend on interest rates, income tax bands, the Personal Savings Allowance, whether the saver is a basic-rate, higher-rate or additional-rate taxpayer, and whether the money is needed soon.

MoneySavingExpert’s Cash ISA guidance focuses heavily on whether the tax-free wrapper is worthwhile compared with ordinary savings rates, because the answer depends on a person’s tax position and available rates (MoneySavingExpert, 2026). Adding a separate 22% charge inside part of a Stocks and Shares ISA creates yet another calculation.

The reported rule also means the charge would not behave like normal savings tax for every person. A basic-rate taxpayer, a higher-rate taxpayer and a non-taxpayer could all see the same 22% deduction on affected cash interest inside the wrapper. That may be administratively neat, but it is not intuitive for households trying to understand whether an ISA is still tax-free.

This is where policy design meets real household behaviour. If a saver needs to compare a reduced Cash ISA limit, the Personal Savings Allowance, ordinary savings rates, investment risk and a special cash charge inside a Stocks and Shares ISA, many will default to doing nothing. For a reform designed to increase participation, inertia is a serious problem.

What UK savers should do now

As of June 2026, the current ISA rules still apply, and the planned changes are not due until April 2027. Savers should avoid rushed decisions based on headlines alone. Check whether money in a Stocks and Shares ISA is genuinely uninvested cash, whether it is there temporarily, and whether it would be better placed in a Cash ISA, an ordinary savings account or diversified investments.

For short-term goals and emergency funds, cash may still be suitable. For long-term goals, a Stocks and Shares ISA can still be useful, provided the investor accepts market risk and chooses investments carefully. Any rates, allowances and product terms mentioned here are current as of June 2026; verify current terms with HMRC, the relevant provider or an FCA-authorised adviser before deciding.

Tax rules and allowances can change each tax year. This article is general education, not regulated financial advice. Nexzoe is not authorised by the FCA. If the decision affects a large amount of money, tax planning, retirement income or your wider financial position, consider speaking to an FCA-authorised Independent Financial Adviser or a qualified tax adviser.