What is an ISA?
An Individual Savings Account (ISA) is a tax wrapper. Put money inside it and the interest, dividends and capital gains you earn are free of UK tax, with nothing to declare on a tax return. For the 2025/2026 tax year, the total ISA allowance is £20,000.
That £20,000 is a use-it-or-lose-it annual limit. Unused allowance does not carry forward. Every 5 April, whatever you did not use disappears.
Types of ISAs Available
- . Cash ISA - Tax-free interest on savings
- . Stocks and Shares ISA - Tax-free growth and dividends on investments
- . Lifetime ISA - 25% government bonus for first home or retirement
- . Innovative Finance ISA - Tax-free returns on peer-to-peer lending
The Change That Matters for 2025/2026
Since April 2024, you can open and pay into multiple ISAs of the same type in a single tax year. Before that, you were restricted to one of each type per year. Now you can spread your Cash ISA allowance across two or three providers to chase the best rates without picking a single account.
Your total contributions across all ISAs still cannot exceed £20,000 in the tax year. The change gives you flexibility, not extra headroom.
How to Make the Most of Your Allowance
Fund it early in the tax year. A contribution made in April 2025 has 12 months longer to grow than one made in March 2026, and for a Stocks and Shares ISA in a global index fund that timing gap compounds into a meaningful sum over decades.
If you cannot invest the full £20,000, set up a regular monthly contribution instead. It puts money in steadily and removes the temptation to time the market.
One clear steer: for money you will not need for at least five years, a Stocks and Shares ISA beats a Cash ISA over that horizon. Cash rates look attractive today, but they have lagged equity returns over long periods. The trap is treating a Cash ISA as a long-term investment when it is a short-term savings tool.
The Lifetime ISA earns its place if you are aged 18 to 39 and saving for a first home or retirement. The 25% government bonus on contributions up to £4,000 a year is a guaranteed return. The catch: withdraw the money for anything other than a first home or retirement after age 60 and you pay a 25% withdrawal charge, which claws back the bonus and a little more.