An ISA is a UK savings account where the interest you earn is not taxed

ISA stands for Individual Savings Account. It is a type of savings account offered by UK banks and building societies. The defining feature is that any interest you earn on the money you deposit is tax-free — you do not pay income tax on those earnings, even if you earn a large amount of interest in a single year.

This is different from a standard savings account, where interest counts as taxable income. The tax exemption applies only to the interest itself, not to the money you deposit. You can withdraw your savings whenever you want, just like a regular account.

ISAs are available only to UK residents aged 16 or older (18 or older for some types). You can hold only one ISA of each type per tax year, though you can switch providers if you want to move your money.

Key Takeaways

  • Interest earned in an ISA is completely tax-free, so you keep all the interest your money makes.
  • You can deposit up to £20,000 per tax year across all your ISAs combined, regardless of type.
  • There are four main types of ISA — Cash ISA, Stocks and Shares ISA, Innovative Finance ISA, and Lifetime ISA — each with different rules about what you can hold.
  • You must be a UK resident and at least 16 years old to open an ISA, though some types require you to be 18.
  • Your money is not locked away; you can withdraw it whenever you need it, though some ISAs may have notice periods or penalties.

The four types of ISA and what each one holds

A Cash ISA works like a regular savings account — you deposit money and earn interest. The only difference is that interest is tax-free. Cash ISAs are offered by most high street banks and building societies. Interest rates vary between providers, and some accounts require a minimum deposit.

A Stocks and Shares ISA lets you invest your money in stocks, bonds, funds, and other investments rather than holding it as cash. You pay no tax on any gains, dividends, or interest from these investments. This type carries investment risk — the value of your money can go down as well as up — and is managed either by you directly or by a fund manager.

An Innovative Finance ISA (sometimes called a Peer-to-Peer ISA) lets you lend money to individuals or small businesses through peer-to-peer lending platforms. The interest you earn is tax-free, but this type carries higher risk because borrowers may default on their loans.

A Lifetime ISA is designed for people aged 18 to 39 who are saving to buy their first home or for retirement. You can deposit up to £4,000 per tax year, and the government adds a 25% bonus (up to £1,000 per year). Money must stay in the account until age 60, or you face a withdrawal penalty, unless you are using it to buy a first home.

How the £20,000 annual deposit limit works

You can pay in up to £20,000 per tax year across all your ISAs combined. This is a single limit that applies to every ISA you hold, not £20,000 per account. If you put £10,000 into a Cash ISA and £8,000 into a Stocks and Shares ISA in the same tax year, you have used £18,000 of your allowance and can deposit only £2,000 more across all accounts.

The tax year runs from 6 April to 5 April the following year. Any money you do not deposit in one year does not roll over — if you deposit only £15,000 in one tax year, you cannot deposit £25,000 the next year. Each year starts fresh with a new £20,000 allowance.

If you hold a Lifetime ISA, the £4,000 annual limit for that account counts toward your overall £20,000 limit. So if you deposit £4,000 into a Lifetime ISA, you can deposit only £16,000 into other ISAs that same tax year.

Tax-free interest and how it affects your tax return

Interest earned in an ISA does not count as taxable income. You do not report it on your Self Assessment tax return, and it does not affect your Personal Savings Allowance or your tax-free Personal Allowance. This is true regardless of how much interest you earn — even if you earn £5,000 in interest, you owe no tax on it.

This tax exemption is the main reason people use ISAs. For someone in the higher tax bracket (40% or 45%), the tax saving can be substantial. For example, if you earn £1,000 in interest on a standard savings account, a higher-rate taxpayer would owe £400 in tax. In an ISA, that same £1,000 is entirely yours.

The tax-free status applies only to interest and investment gains. If you deposit money into an ISA, that money itself is not tax-deductible — you cannot claim it as a deduction on your tax return.

Opening an ISA and switching between providers

You open an ISA by contacting a bank, building society, or investment platform that offers them. Most high street banks offer Cash ISAs; investment platforms and peer-to-peer lenders offer the other types. You will need to prove your identity and UK residency, usually by providing a passport or driving licence and a recent utility bill or bank statement.

You can hold only one ISA of each type per tax year. If you want to switch to a different provider — for example, to get a better interest rate on your Cash ISA — you can do so, but you must use the formal transfer process. Ask your new provider to arrange the transfer; they will handle the paperwork with your old provider. Do not simply withdraw the money and deposit it elsewhere, because that counts as a new deposit and uses part of your annual allowance.

If you have held an ISA with a provider in a previous tax year and want to open a new one with them in the current year, you can do that — the one-per-type rule applies only within a single tax year.

Withdrawals, notice periods, and access to your money

Cash ISAs typically allow you to withdraw money whenever you want, with no penalty. Some accounts have a notice period — you might need to give 30 or 60 days' notice before withdrawing a large sum — but this varies by provider. Check the terms of your specific account before opening it.

Stocks and Shares ISAs and Innovative Finance ISAs may have longer notice periods or may require you to sell investments before you can access the cash. Peer-to-peer lending platforms may not allow you to withdraw money until loans are repaid, which can take months or years.

Lifetime ISAs have strict withdrawal rules. You can withdraw money penalty-free only if you are buying your first home (up to age 39) or if you reach age 60. If you withdraw for any other reason before age 60, you lose the government bonus and pay a 25% withdrawal charge on the bonus itself. For example, if you received a £1,000 bonus and withdraw early, you lose the £1,000 and pay an additional £250 charge.

ISAs versus regular savings accounts and other options

The main advantage of an ISA over a regular savings account is the tax exemption on interest. For someone earning significant interest, this can save hundreds of pounds per year. However, ISAs are not always the best choice for everyone.

If you earn very little interest — for example, because interest rates are low or your balance is small — the tax saving may be minimal. Many people have a Personal Savings Allowance that lets them earn a certain amount of interest tax-free anyway. Basic-rate taxpayers can earn up to £1,000 in interest tax-free; higher-rate taxpayers can earn up to £500 tax-free. If your interest falls within these allowances, an ISA offers no extra benefit.

Stocks and Shares ISAs offer tax-free investment growth, but they carry investment risk. A regular Stocks and Shares investment account (not an ISA) offers the same investments but with tax on gains and dividends. For someone investing small amounts or for short periods, the tax savings may not outweigh the investment risk.

Premium Bonds and some NS&I accounts offer tax-free returns without an annual deposit limit, though the returns are typically lower and less predictable than interest-bearing accounts.

Frequently Asked Questions

Can I have more than one ISA?

You can hold one ISA of each type per tax year — one Cash ISA, one Stocks and Shares ISA, one Innovative Finance ISA, and one Lifetime ISA. You cannot hold two Cash ISAs in the same tax year, but you can switch to a different provider if you want a better rate. Once the tax year ends, you can open a new ISA with a different provider.

What happens to my ISA if I move abroad?

You must be a UK resident to open an ISA. If you move abroad, you can no longer pay into your ISA, and any new interest earned may become taxable. You should contact your ISA provider to discuss your options; some allow you to keep the account open but frozen, while others require you to close it.

Do I need to report my ISA on my tax return?

No. ISA interest and investment gains do not need to be reported to HMRC or included on a Self Assessment tax return. The tax-free status is automatic — you do not need to do anything to claim it.

Can I transfer money between different types of ISA?

You cannot move money directly from one type of ISA to another. If you want to move money from a Cash ISA to a Stocks and Shares ISA, you must withdraw it (which counts as using part of your annual allowance) and deposit it as a new payment. The exception is if you are switching providers — your new provider can arrange a transfer that does not count against your allowance.

What is the difference between an ISA and a Junior ISA?

A Junior ISA is for children under 16 (or under 18 for some types) and is managed by a parent or guardian. The child cannot access the money until age 16 or 18. An ISA is for adults aged 16 or older who manage their own account. The tax-free interest rules are the same for both.