Home › Calculator Hub › Cash ISA Calculator
ISAProject tax-free growth inside a Cash ISA and compare directly against a taxable savings account at the same rate. The gap is bigger than most people think once your PSA is used up.
Runs entirely in your browser — your numbers are never sent to a server.
Inside a Cash ISA, interest is never taxed and never counts towards your PSA. Outside, interest above your PSA (£1,000 basic, £500 higher, £0 additional) is taxed at your marginal rate.
A higher-rate taxpayer with over around £11,000 non-ISA savings at today's rates already pays tax. Additional-rate taxpayers pay from the first pound.
£20,000 per adult per tax year across all ISA types combined. Resets on 6 April. Unused allowance does not carry forward.
Always, if you expect to exceed your PSA. Even for basic-rate taxpayers under PSA today, future rate rises could push them over — ISA money stays tax-free regardless.
No. ISA interest and PSA are separate — you get both in full.
No — the cap applies across all your ISAs combined.
Yes since April 2024, but the £20,000 total still applies.
Illustrative calculation. Not personalised financial advice. Rates, bands and allowances for the 2026/27 UK tax year, verified against gov.uk at time of review. For regulated advice consult an FCA-authorised adviser.