ISA Calculator

See how your Cash ISA could grow with real rates, monthly contributions, and a year-by-year projection.

100% Tax-Free Interest

Every penny of interest in a Cash ISA is exempt from income tax — no matter how much you earn.

£20,000 Allowance (2026/27)

Save up to £20,000 across all your ISAs this tax year. Unused allowance doesn't carry over.

FSCS Protected to £120,000

Your Cash ISA savings are protected per authorised firm up to the current FSCS limit.

Your inputs

£5.0k
£0£20,000 limit

25% of your 2026/27 allowance used

£200/mo
£0£1,000/mo
4.50%
0.1%7.0%
5 years
1 year20 years

Estimates only. Monthly compounding assumed. Illustrative — not advice.

Final ISA balance

£19,688.09

Tax-free interest earned

£2,688.09

Total you put in

£17,000.00

Est. tax saved (20%)

£537.62

Year-by-year growth

Monthly compounding

This calculator provides illustrative estimates only using monthly compounding. Actual returns depend on your provider's terms, interest calculation method, and any rate changes. The £20,000 annual ISA allowance applies to the 2026/27 tax year. Consult a financial adviser for personal advice.

Understanding Cash ISAs

What is a Cash ISA?

A Cash ISA is a tax-free savings account available to UK residents. Any interest you earn is completely free from income tax, making it one of the most straightforward ways to shelter savings from the taxman.

2026/27 ISA Allowance

You can save up to £20,000 across all your ISA accounts this tax year. This covers Cash ISAs, Stocks and Shares ISAs, Lifetime ISAs, and Innovative Finance ISAs. The allowance resets on 6 April each year.

Types of Cash ISA

Cash ISAs come in easy access (withdraw anytime), fixed rate (lock in for 1–5 years), and notice account flavours. Easy access tends to have lower rates; fixed rate ISAs offer certainty in return for less flexibility.

ISA vs Regular Savings

Regular savings accounts may attract tax on interest above your Personal Savings Allowance (£1,000 for basic rate taxpayers; £500 for higher rate). ISA interest is always tax-free — which makes ISAs particularly valuable for higher earners or larger pots.

Find the Best Cash ISA Rates

Compare live rates from UK Cash ISA providers and start earning tax-free today.

Compare ISA Rates
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