A cash ISA is a savings account where interest is normally free from UK income tax, while interest from an ordinary savings account may count towards your Personal Savings Allowance. Which is better depends on the interest rate, your tax band, how much you have saved and whether you need easy access. Cash ISAs have an annual ISA allowance, currently £20,000 across all your ISAs, and some accounts may charge or restrict withdrawals. Compare the terms and rates from FCA-authorised providers, and check GOV.UK for the latest tax rules.