What Is an ISA? A Plain-English Guide to Individual Savings Accounts
Published 9th of March 2011·Updated 5 April 2026
Reviewed by: Reviewed for accuracy April 2026
An ISA (Individual Savings Account) is a tax-free wrapper that shelters your savings or investments from income tax and capital gains tax. Any interest, dividends or growth earned inside an ISA is yours to keep in full. In the 2025-26 tax year, you can pay in up to £20,000 across all your ISAs combined.
Short Summary
Every UK adult aged 18 or over can save up to £20,000 into ISAs each tax year. The tax year runs from 6 April to 5 April. Any unused allowance cannot be carried forward; if you do not use it, you lose it.
There are four main types of ISA: Cash ISA, Stocks and Shares ISA, Innovative Finance ISA, and Lifetime ISA. You can split your £20,000 allowance between them in any combination, subject to the Lifetime ISA's internal cap of £4,000.
Interest earned inside a Cash ISA is completely tax-free and does not count against your Personal Savings Allowance. This matters most for higher-rate and additional-rate taxpayers, who pay 40 per cent or 45 per cent tax on savings interest outside an ISA.
Your ISA savings are protected up to £85,000 per authorised institution under the Financial Services Compensation Scheme (FSCS), the same as any other bank or building society account.
What types of ISA are available in the UK?
| ISA type | What it invests in | Annual limit | Key rule |
|---|---|---|---|
| Cash ISA | Cash savings | Up to £20,000 | Interest is tax-free |
| Stocks and Shares ISA | Shares, funds, bonds | Up to £20,000 | Returns are tax-free |
| Innovative Finance ISA | Peer-to-peer loans | Up to £20,000 | Higher risk, less protection |
| Lifetime ISA (LISA) | Cash or investments | Up to £4,000 | 25% government bonus; for first home or retirement |
| Junior ISA | Cash or investments | £9,000 (separate) | For under-18s; parents manage it |
You can open one of each type in a single tax year. The total you pay in across all ISAs (except the Junior ISA, which has its own allowance) cannot exceed £20,000.
How does a Cash ISA work?
A Cash ISA works like a standard savings account, except the interest you earn is completely free of income tax. You open one with a bank or building society, deposit money up to the annual limit, and earn interest at the account's stated rate.
Easy-access Cash ISAs allow withdrawals at any time. Fixed-rate Cash ISAs lock your money away for a set term (typically one or two years) in exchange for a higher guaranteed interest rate. Some ISAs are "flexible", meaning you can withdraw and replace money in the same tax year without it counting twice against your allowance; not all providers offer this, so check the terms.
In April 2026, the best easy-access Cash ISAs are paying around 4.5 per cent per year. Providers including Marcus (by Goldman Sachs), Moneybox, and several building societies consistently offer competitive rates. Compare current rates at MoneySavingExpert.com or MoneySuperMarket.com.
What is a Stocks and Shares ISA?
A Stocks and Shares ISA allows you to invest in shares, funds, investment trusts, bonds and other assets while sheltering all returns from tax. You pay no capital gains tax on profits and no income tax on dividends, regardless of how much your investments grow.
Investment platforms including Hargreaves Lansdown, Vanguard, AJ Bell and Fidelity all offer Stocks and Shares ISAs with varying fee structures. Vanguard's ISA charges 0.15 per cent of your portfolio per year (capped at £375 for portfolios over £250,000), making it one of the lowest-cost options for fund investors.
Stocks and Shares ISAs carry investment risk; the value of your investments can fall as well as rise. They are generally suited to money you can leave invested for at least five years, which gives time to recover from short-term market falls.
What is a Lifetime ISA and should I use one?
A Lifetime ISA is designed for two purposes only: buying your first home, or saving for retirement from age 60. You can open one if you are aged 18 to 39. You can pay in up to £4,000 per year and the government adds a 25 per cent bonus on top, worth up to £1,000 per year.
To use the money for a first home purchase, the property must cost no more than £450,000 and you must have held the LISA for at least 12 months. If you withdraw for any other reason before age 60, a withdrawal charge of 25 per cent applies, which effectively clawing back the government bonus plus a small additional penalty.
For first-time buyers, the Lifetime ISA is one of the most generous government savings incentives available. MoneyHelper at moneyhelper.org.uk provides a full comparison of the LISA against the Help to Buy ISA (now closed to new applicants).
Can I transfer my ISA to a different provider?
Yes. You can transfer a Cash ISA to another Cash ISA, or to a Stocks and Shares ISA, at any time. You can also transfer a Stocks and Shares ISA to a Cash ISA. The transfer must be done formally through the receiving provider; withdrawing cash yourself and depositing it elsewhere counts as a new subscription and uses your current year's allowance.
A good-quality provider should complete an ISA transfer within 15 working days for cash ISAs, according to HMRC guidelines. If a transfer takes longer than this without explanation, contact the receiving provider and, if necessary, the Financial Ombudsman Service.
How much could I save in an ISA over time?
Consistently using your ISA allowance is one of the most tax-efficient things most UK adults can do. The following illustrates the long-term benefit of regular ISA saving, assuming a 5 per cent annual return:
| Monthly deposit | After 10 years | After 20 years | After 30 years |
|---|---|---|---|
| £100 | £15,593 | £41,103 | £83,226 |
| £300 | £46,778 | £123,309 | £249,677 |
| £500 | £77,964 | £205,516 | £416,129 |
| £1,000 | £155,929 | £411,033 | £832,258 |
Returns shown are illustrative. Actual returns on Stocks and Shares ISAs depend on investment performance and are not guaranteed. Cash ISA returns depend on prevailing interest rates, which change over time.
Frequently Asked Questions
How many ISAs can I have at the same time?
You can hold as many ISAs as you like from previous tax years. In any single tax year, you can open and pay into one Cash ISA, one Stocks and Shares ISA, one Innovative Finance ISA, and one Lifetime ISA simultaneously, provided your total subscriptions across all four do not exceed £20,000 (with the LISA capped at £4,000 within that total).
What happens if I pay more than the ISA allowance by mistake?
HMRC will write to you if you exceed the annual ISA limit. The excess amount loses its tax-free status and HMRC may instruct the ISA provider to return it. To avoid this, track your contributions carefully if you hold multiple ISAs. Your bank or ISA provider should notify you if you are approaching your limit.
Can I open an ISA for my child?
Yes, through a Junior ISA. Children under 18 can have a Cash Junior ISA, a Stocks and Shares Junior ISA, or both. The annual limit for Junior ISAs in 2025-26 is £9,000. Parents or guardians manage the account; the child can take control at 16 but cannot withdraw the money until they turn 18, when it automatically converts to an adult ISA.
Do I lose my ISA if I move abroad?
No. You keep your existing ISAs and the funds within them remain tax-free. However, you cannot pay new money into a UK ISA once you are no longer UK resident for tax purposes. If you return to the UK, you can resume contributing in the tax year your UK residency resumes.
Is my money safe inside an ISA?
Cash ISAs are protected by the FSCS up to £85,000 per authorised institution, the same as any savings account. Stocks and Shares ISAs are protected up to £85,000 per firm under the FSCS if the investment firm fails or misappropriates your assets; however, investment losses due to normal market movements are not covered. The FSCS website at fscs.org.uk explains the coverage in detail.