Cash ISAs
How cash ISA interest works, what affects rates and how a cash ISA differs from other savings.
For information only, not financial advice.
Guides on cash ISAs: how the interest is worked out, what moves rates, how cash ISAs compare with investing in a stocks and shares ISA, and how they sit alongside other savings. Rates change often, so the calculators ask you to type the rate you are looking at.
Quick answers
Is interest on a cash ISA taxed?
gov.uk says you do not pay tax on interest on cash in an ISA. Interest on savings outside an ISA can be taxable, depending on income and the Personal Savings Allowance; the ISA vs Savings Account Calculator shows the difference for figures you enter.
What is the cash ISA limit?
Regulations made on 10 September 2026 (SI 2026/1018, read on legislation.gov.uk on 6 October 2026) provide that from 6 April 2027, savers who are under 65 at the end of the tax year will be able to pay up to £12,000 a year into cash ISAs, within the overall ISA allowance. From the start of the tax year in which they turn 65, savers will be able to pay up to £20,000 a year into cash ISAs. The overall allowance of £20,000 still applies across all ISAs.
Rules data last checked against gov.uk on 26 September 2026. For information only, not financial advice.
Tools for this topic
Cash ISA Calculator
Estimate the interest a cash ISA could earn at a rate you choose.
ISA vs Savings Calculator
Compare a cash ISA with a taxable savings account.
Fixed-Rate ISA Switch Calculator
Compare an early access penalty with the extra interest a higher rate could earn.
Guides
- Cash ISA Interest: Worked Examples at Different Rates
See how Cash ISA interest is worked out, with tables for £6,000, £10,000 and £15,000 at assumed rates, plus a five-year example with monthly payments.
- How Do Interest Rates Affect a Cash ISA?
How Bank of England rate changes can feed through to Cash ISA interest, with worked examples at assumed rates and notes on fixed and variable accounts.
- What Drives Cash ISA Growth Rates?
What sets Cash ISA growth rates, how Bank of England Bank Rate feeds through, and a worked example at assumed rates. Not a forecast.
- Cash ISA vs Stocks and Shares ISA: What Is the Difference?
How Cash ISAs and Stocks and Shares ISAs differ on risk, access, protection and the new cash ISA limit, with the points people weigh up.
- Cash ISA changes from April 2027: £12,000 limit explained
Regulations made in 2026 set a £12,000 cash ISA limit from 6 April 2027, not yet in force, for savers under 65 at the end of the tax year. Who is exempt.
- ISAs and Premium Bonds: How Each Works
A neutral, factual look at how ISAs and Premium Bonds work: what you receive, tax, limits and access, with sources.
See also the ISA rules at a glance, the ISA glossary and all topics.