What if I'd maxed my ISA allowance every year?

Every UK adult gets a £20,000 annual ISA allowance — investments inside grow completely tax-free. Move the sliders to see what consistently using that allowance could illustratively mean over time.

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Annual ISA contribution £10,000

Current annual ISA allowance: £20,000 per person

Age you started 30
Age you'd access it 60
Assumed annual growth rate 7%
Your ISA could illustratively be worth
£944,000
30 years at £10,000/year · 7% growth · all tax-free — for illustration only
Total contributed
£300,000
Tax-free growth
£644,000
Growth multiplier
3.1×
What you put in
£300,000
Total ISA value
£944,000
Same — no ISA wrapper
est. less

Contributing £10,000/year to a Stocks & Shares ISA from age 30 could illustratively grow to £944,000 by 60 — all completely tax-free. Outside an ISA wrapper, gains above your Capital Gains Tax annual exempt amount would be subject to CGT, potentially reducing your net return.

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What's special about an ISA?

An Individual Savings Account (ISA) is a government-backed tax wrapper available to UK adults. Any growth, interest, or dividends earned inside an ISA are completely free from UK Income Tax and Capital Gains Tax — both while it grows and when you withdraw. You can put up to £20,000 in per tax year (2024/25 allowance). Unused allowance doesn't carry over.

A Stocks & Shares ISA invests your money in the stock market. Returns are not guaranteed and the value can fall as well as rise. The tax-free benefit is the wrapper — not the investment itself. The 7% default growth rate in this calculator is a commonly referenced long-run average for diversified global equities; actual returns will vary.

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Illustrative purposes only. This calculator does not constitute financial advice. ISA tax rules are subject to change. The £20,000 annual allowance applies for the 2024/25 tax year. Growth rates are not guaranteed. Stocks and shares investments can fall as well as rise. For personalised ISA advice, consult an FCA-authorised financial adviser.