UK Cash ISA Compound Growth & Tax Shelter Calculator (2026/27)
Shelter up to £20,000 per tax year inside a UK Cash ISA in 2026/27 so 100% of your compound interest remains permanently free from UK Income Tax.
| ISA Balance (5.0% AER) | Annual Tax-Free Interest | Higher-Rate Tax Saved (vs Non-ISA) |
|---|---|---|
| £20,000 (1-Year Allowance) | £1,000 / year | £200 / year saved after £500 PSA |
| £40,000 (2-Year ISA Pot) | £2,000 / year | £600 / year saved (40% band) |
| £60,000 (3-Year ISA Pot) | £3,000 / year | £1,000 / year saved (40% band) |