See how much your ISA could grow with regular saving. Enter your current balance, how much you pay in each month and the interest or growth rate you expect, and this calculator shows your tax-free ISA value over time, keeping within the £20,000 yearly ISA allowance.
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ISA allowance 2026/27
You can put up to £20,000 into ISAs in the 2026/27 tax year (6 April 2026 to 5 April 2027). You can split it across different types of ISA, and any interest, dividends or growth is free of UK tax. Unused allowance does not carry over to the next year.
| Type of ISA | What it is |
|---|---|
| Cash ISA | A savings account with tax-free interest |
| Stocks and shares ISA | Investments in funds, shares and bonds with tax-free growth |
| Lifetime ISA | For first homes or retirement, open before age 40, with a government bonus |
| Innovative finance ISA | Peer-to-peer lending and similar investments |
Frequently asked questions
How much will £300 a month in an ISA be worth after 10 years?
Starting from £5,000 and adding £300 a month at 4.5% a year, an ISA would be worth about £52,900 after 10 years. You would have paid in £36,000 of that, with the rest coming from tax-free interest or growth.
Is a cash ISA or a stocks and shares ISA better?
A cash ISA keeps your money safe and is better for savings you may need within a few years. A stocks and shares ISA can grow more over the long term, but its value can fall as well as rise.
Are ISA rules changing?
The government has announced changes to cash ISA limits from April 2027. The overall £20,000 allowance applies for 2026/27. Check GOV.UK for the latest rules before you plan future years.
ISA allowance from GOV.UK. Interest and growth rates are not guaranteed. For illustration only, not financial advice. Related: UK pension calculator · Savings goal calculator