UK ISA Calculator
Project the tax-free growth of your ISA contributions up to the £20,000 annual allowance.
Details
Result
ISA Value
£232,176
Total Contributed
£120,000
Tax-Free Gains
£112,176
Tax Saved (vs GIA)
£22,435
What is an ISA?
An ISA (Individual Savings Account) shelters up to £20,000/year of savings or investments from UK Income Tax and Capital Gains Tax. Returns compound tax-free — crucial over 10-30 year horizons where CGT would otherwise eat 10-20% of gains.
Cash ISA vs Stocks & Shares ISA
Cash ISAs are safe but lag inflation. Stocks & Shares ISAs are volatile year-to-year but historically return 7-9% p.a. over the long term. Use Cash for short-term goals (<5 years) and S&S for long-term wealth building.
Frequently Asked Questions
Everything you need to know, in one place.
What is the ISA annual allowance?
£20,000 per tax year (6 April – 5 April). Can be split across Cash ISA, Stocks & Shares ISA, Lifetime ISA (£4k), and Innovative Finance ISA. All gains and withdrawals are tax-free.
Cash ISA vs Stocks & Shares ISA?
Cash ISA: safe, but returns may lag inflation (4-5% in 2026). Stocks & Shares ISA: volatile but historical 7-9% real returns over 10+ years. Horizon under 5 years → Cash. Longer → Stocks.
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