ISAs are the UK's most powerful tax shelter for investments. All growth, dividends, and interest are completely tax-free — no capital gains tax, no dividend tax, no income tax on withdrawals.
This calculator projects your ISA balance over time with regular contributions up to the annual allowance (£20,000). See how tax-free compounding outperforms a taxable account over 10, 20, or 30 years, and understand the real cost of not using your ISA allowance.
Use it to plan your annual ISA contributions, compare cash ISA versus stocks & shares ISA returns, and see the long-term benefit of maxing out your allowance each year.
Inputs
Results
Projected Balance after 20 Years
£221,582
Total Contributions
£125,000
Total Growth
£96,582
Year-by-Year Breakdown
| Year | Contribution | Growth | Balance |
|---|---|---|---|
| 1 | £6,000 | £550 | £11,550 |
| 2 | £6,000 | £878 | £18,428 |
| 3 | £6,000 | £1,221 | £25,649 |
| 4 | £6,000 | £1,582 | £33,231 |
| 5 | £6,000 | £1,962 | £41,193 |
| 6 | £6,000 | £2,360 | £49,553 |
| 7 | £6,000 | £2,778 | £58,330 |
| 8 | £6,000 | £3,217 | £67,547 |
| 9 | £6,000 | £3,677 | £77,224 |
| 10 | £6,000 | £4,161 | £87,385 |
| 11 | £6,000 | £4,669 | £98,054 |
| 12 | £6,000 | £5,203 | £109,257 |
| 13 | £6,000 | £5,763 | £121,020 |
| 14 | £6,000 | £6,351 | £133,371 |
| 15 | £6,000 | £6,969 | £146,340 |
| 16 | £6,000 | £7,617 | £159,957 |
| 17 | £6,000 | £8,298 | £174,254 |
| 18 | £6,000 | £9,013 | £189,267 |
| 19 | £6,000 | £9,763 | £205,030 |
| 20 | £6,000 | £10,552 | £221,582 |
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