A Cash ISA (Individual Savings Account) is a UK savings account that allows you to earn interest free from UK Income Tax. It works much like a conventional savings account, but with additional tax advantages. Understanding how Cash ISAs work can help you decide whether they're the right home for your savings.
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A Cash ISA works in much the same way as an ordinary savings account. You deposit money with a bank or building society, and the provider pays interest on your balance. The main difference is that interest earned within a Cash ISA is free from UK Income Tax, regardless of how much interest you receive. Cash ISAs are available in several forms, including easy-access accounts, fixed-rate accounts and notice accounts. Each has different rules about withdrawing money, interest rates and how long you may need to leave your savings untouched.
The annual ISA allowance determines how much you can pay into ISAs during each tax year, which runs from 6 April to 5 April. For the 2026/27 tax year, the overall ISA allowance is £20,000 for eligible adults. This allowance is shared across Cash ISAs, Stocks and Shares ISAs, Innovative Finance ISAs and Lifetime ISAs, rather than being a separate allowance for each account. You can pay into more than one ISA during the tax year, subject to the applicable rules and limits. Unused ISA allowance cannot be carried forward into the next tax year.
Changes coming in April 2027
From 6 April 2027, the annual Cash ISA contribution limit will reduce to £12,000 for savers under 65. Those aged 65 and over will retain a £20,000 Cash ISA limit. The overall annual ISA allowance will remain £20,000. Additional rules will also affect certain transfers between ISA types.
Whether you can withdraw money depends on the type of Cash ISA you choose. Easy-access Cash ISAs generally allow withdrawals whenever you need your money, although some accounts restrict the number of withdrawals or reduce the interest rate if you withdraw too frequently. Fixed-rate Cash ISAs typically require you to leave your money untouched for an agreed period. Early withdrawals may be prohibited or subject to an interest penalty. Some Cash ISAs are described as flexible. With a flexible ISA, you can withdraw money and replace it within the same tax year without the replacement counting towards your annual ISA allowance, provided you follow the provider's rules. Not every Cash ISA is flexible, so always check the account terms before withdrawing money.
Cash ISAs provided by UK-authorised banks and building societies generally benefit from protection under the Financial Services Compensation Scheme (FSCS).Eligible deposits are protected up to £120,000 per person, per authorised institution. This limit applies to your combined eligible deposits with that institution, not separately to each account or Cash ISA. Some banking brands share the same banking licence, so it is worth checking whether your savings are held with the same authorised institution. FSCS protection covers eligible deposits if an authorised institution fails. It does not guarantee that your interest rate will remain competitive.
The biggest difference between a Cash ISA and an ordinary savings account is how the interest is taxed. Interest earned within a Cash ISA is free from UK Income Tax. Interest earned in an ordinary savings account may be taxable, although many savers can earn some interest tax-free through their Personal Savings Allowance. Basic-rate taxpayers generally have a £1,000 Personal Savings Allowance, while higher-rate taxpayers have £500. Additional-rate taxpayers do not receive a Personal Savings Allowance. This means a Cash ISA is not automatically the best choice for everyone. If you are unlikely to pay tax on your savings interest, an ordinary savings account offering a higher interest rate could provide a better return.
Yes. You can transfer an existing Cash ISA to another provider, which can be useful if you find a better interest rate or an account that suits your needs more closely. The important thing is to use the new provider's official ISA transfer process rather than withdrawing the money yourself. This helps preserve the tax-free status of your savings. Before transferring, check whether your existing provider charges an early withdrawal or transfer penalty, particularly if you have a fixed-rate account. Also check whether the new provider accepts ISA transfers.
The best Cash ISA for you depends on how much you want to save, when you might need the money and whether you prefer a fixed or variable interest rate. Compare the Annual Equivalent Rate (AER), which helps you understand the annual interest return, as well as any restrictions on withdrawals, minimum deposits and introductory rates. If you might need your savings at short notice, an easy-access Cash ISA may be more suitable. If you can leave your money untouched for a set period, a fixed-rate Cash ISA may offer greater certainty about the interest you will earn. Remember that the account offering the highest interest rate isn't necessarily the best choice if its restrictions don't suit your circumstances.
A Cash ISA can be particularly valuable if you have substantial savings, expect to exceed your Personal Savings Allowance or simply want to protect your savings interest from UK Income Tax. However, ordinary savings accounts can sometimes offer higher interest rates. If you are unlikely to pay tax on your savings interest, comparing both options may help you achieve a better return. The right decision depends on your personal circumstances, the interest rates available and how you intend to use your savings.
Yes. You can hold multiple Cash ISAs and, under the current rules, pay into more than one during the same tax year, subject to the applicable ISA limits and provider conditions.
No. Money withdrawn from a Cash ISA is not subject to UK Income Tax simply because you withdraw it. However, replacing withdrawn money without using additional ISA allowance depends on whether your account is flexible.
Cash ISAs do not expose your savings to stock market fluctuations. Eligible deposits with UK-authorised institutions generally benefit from FSCS protection, subject to its limits. However, inflation can reduce the purchasing power of your savings over time.
Yes. Many banks and building societies allow you to open and manage Cash ISAs online, although some providers also offer branch or postal applications.
Explore different Cash ISA options and compare interest rates, withdrawal rules and account features to help you find an account that suits your savings goals.
Compare Cash ISAsFor more information about ISA eligibility, allowances and tax rules, visit the UK government's official ISA guidance. You can also check how your savings are protected through the Financial Services Compensation Scheme (FSCS).