How an ISA works

An Individual Savings Account, or ISA, is a tax-advantaged savings product providing relief from tax to individuals¹. In plain terms, it is a wrapper you put savings or investments inside so that the returns escape tax: income you earn from an ISA is not taxable², and the money remains free from UK Income Tax and Capital Gains Tax for as long as you keep it there³. You do not declare ISA income on a tax return and nothing is deducted at source.

Each tax year you can pay in up to the overall annual ISA limit of £20,000, spread across cash, stocks and shares and innovative finance ISAs in whatever mix you choose⁴. There are four main types of adult ISA: the cash ISA, the stocks and shares ISA, the Innovative Finance ISA and the Lifetime ISA⁵, plus the Junior ISA for under-18s. The rules on how many accounts you can hold, and how much can go into a cash ISA, are changing, and this page sets out how each type works, what it costs to use, and what happens when you take money out.

What an ISA is and what it offers

The legislation describes an ISA as "a tax-advantaged savings product providing relief from tax to individuals"¹. What that means in practice is that the account itself is ordinary: with a cash ISA the money sits with a bank, building society or National Savings and Investments (NS&I), earning interest, and with a stocks and shares ISA it is invested on the stock markets¹¹. The tax treatment is what makes the wrapper different. Interest, dividends and capital gains inside an ISA escape the tax that would otherwise apply, and the exemption continues for as long as the money stays in ISAs³.

The relief is given automatically. There is no claim to make to HMRC and no box to fill in on a tax return: the ISA manager handles the tax side, and you simply receive whatever the account earns². The legislation allows individuals to save through ISA accounts without being taxed on any income or gains arising from or received in relation to those savings¹².

What an ISA offers, in short, is a way to save or invest without the tax bill. That matters most to people whose savings would otherwise breach the tax-free allowances on savings interest or investment gains, but the wrapper is open to everyone who meets the age and residence conditions, and there is no minimum. The trade-offs come with the detail: some types lock your money in, some carry fees, and one type, the Lifetime ISA, charges a penalty if you withdraw for the wrong reason. The rest of this page works through each type in turn.

Four adult ISAs, plus the Junior ISA

There are four types of ISA available to adults¹¹, and official statistics list the same four: cash ISA, stocks and shares ISA, Innovative Finance ISA and Lifetime ISA⁵. The legislation sets out that an ISA may be set up as a stocks and shares account, a cash account, an innovative finance account or a Lifetime ISA account¹³.

• Cash ISAs work like a tax-free savings account: you pay money in, the provider pays interest, and the interest escapes tax¹¹.
• Stocks and shares ISAs hold money invested on the stock markets, so the value rises and falls with those investments¹¹.
• Innovative Finance ISAs sit alongside these as the third type for adult savers under the ISA regulations¹⁴.
• Lifetime ISAs can hold any type of investment that would qualify for a cash or stocks and shares ISA¹⁴, with qualifying investments the same as for those two types¹⁵. They come with a government bonus and, in return, strict rules on when you can withdraw.
• Junior ISAs are the children's version, available as cash or stocks and shares products¹².

How many accounts you can hold has been relaxed over the years. The position since 6 April 2024 is that you can open and pay into more than one ISA of the same type in a tax year¹⁶, and NS&I's guidance puts it simply: you can open as many different adult ISA accounts as you like, as long as you keep within the ISA allowance rules¹⁷. Earlier legislation, from 2008, allowed a qualifying individual to subscribe to two ISAs in a tax year, one cash and one stocks and shares¹⁸. The documents are not in conflict so much as layered: the older rule set the floor, and the 2024 change removed the one-of-each-type restriction. The Lifetime ISA remains the exception, with only one Lifetime ISA payable into each tax year, and total payments across everything cannot exceed the annual allowance¹⁷.

Age limits differ by type, which is worth checking before you plan your subscriptions. The age at which a cash ISA can be held rose from 16 to 18, except for people who were 16 or 17 on 5 April 2024 and had not yet turned 18, who can continue to have, apply for or transfer a single cash ISA account¹⁹. Who can open each type is covered in full on who can open an ISA.

Cash ISAs: easy access or fixed term

A cash ISA is the closest thing to an ordinary savings account inside the tax wrapper: you deposit money, the provider pays interest, and no tax is deducted¹¹. Within that, providers offer several shapes of account. The main types are easy access cash ISAs, notice cash ISAs, fixed rate cash ISAs, Help to Buy ISAs and Lifetime cash ISAs²⁰.

The choice between them is a trade between access and certainty. An easy access ISA lets you withdraw at any time, usually without charge, but the rate is variable: NS&I, for example, states that the rate on its Direct ISA is variable and can be changed up or down from time to time, for instance when the Bank of England base rate changes or when rates in the general savings market move¹⁶. So when the Bank of England cuts interest rates, variable cash ISA rates often follow, and providers give notice before a fall: NS&I says it will contact customers personally in advance if the rate goes down.

A fixed rate cash ISA gives you an interest rate which stays the same over a set period, typically 1, 2, 3, 4 or 5 years¹⁷. In return for that certainty you give up access: you usually cannot withdraw money during the fixed term without penalty, unless the product rules allow it¹⁷. Notice ISAs sit in between, requiring a set period of notice before each withdrawal²⁰.

The comparison between fixed and easy access accounts, including what happens at maturity, is set out in fixed rate cash ISAs, and the wider choice between an ISA and an ordinary savings account in cash ISAs explained.

Stocks and shares ISAs: investing without tax on gains

A stocks and shares ISA holds money invested on the stock markets rather than in a savings account¹¹. The tax position is the attraction: ISAs are tax exempt accounts, so income received in the form of interest or dividends, and capital gains, escape tax⁵. You can hold funds, shares and other qualifying investments, and the range of eligible investments is the same as would qualify outside the wrapper, as described in what investments a stocks and shares ISA can hold.

Unlike a cash ISA, a stocks and shares ISA usually costs money to run. You may pay fees with this type of ISA, including platform charges, management charges, trading fees and transfer out fees²⁰. Platform charges are typically a percentage of the value held or a flat fee, management charges apply to funds, trading fees apply each time you buy or sell, and transfer out fees can apply if you move the account to another provider. The mix varies widely between platforms, and the fee structure matters as much as the headline figures: a flat fee suits larger pots, a percentage fee smaller ones. The detail is covered in ISA fees and charges.

One tax edge is worth knowing. Interest arising on uninvested cash held in a stocks and shares ISA, money waiting to be invested, is subject to a flat rate charge representing tax at the basic rate²¹. The ISA protects invested money fully; cash parked inside an investment ISA is treated differently.

Because the money is invested on the stock markets, the value of a stocks and shares ISA moves with those markets and can fall as well as rise¹¹. The tax wrapper removes tax on gains; it does nothing to remove investment risk. How these accounts work in practice, including ready-made options for people who do not want to pick investments themselves, is covered in stocks and shares ISAs explained and ready-made and managed ISAs.

The cash ISA limit falls to £12,000 for under-65s from April 2027

The overall annual ISA subscription limit is £20,000 per tax year, across cash, stocks and shares and innovative finance ISAs⁴. Within that, the government is reducing the annual cash ISA subscription limit to £12,000 for individuals aged under 65 from 6 April 2027⁶. The draft legislation frames the restriction by age: it applies in any year in which a qualifying individual is 64 or under at the end of that year²².

People aged 65 and over keep the higher figure. Savers aged 65 and over will continue to be able to save up to £20,000 in a cash ISA each year⁷, and entitlement to the higher limit applies from the start of the tax year in which an individual turns 65²³. So someone whose 65th birthday falls in November begins the tax year already treated as 65 for this purpose.

The change does not reduce the overall £20,000 allowance: money that can no longer go into cash can still go into stocks and shares or innovative finance ISAs, up to the overall limit⁴. The government has also published anti-circumvention rules alongside the reform, aimed at arrangements designed to get around the new cash restriction²⁴. For people aged 16 or 17 on 5 April 2024 who have not since turned 18, the right to continue holding a single cash ISA is preserved¹⁹.

The Lifetime ISA has its own limit inside the overall one: adults under 40 can open a Lifetime ISA and pay in up to £4,000 each tax year⁸, and current year payments by a qualifying individual must be made when the individual is under 50 years of age²⁵. How the new cash limit works, and what it means for savers in each age group, is followed in changes to the cash ISA limit and the ISA allowance.

Lifetime ISA withdrawals can cost 25%

The Lifetime ISA is built around a government bonus paid on your savings, and the withdrawal charge is how the government claws the bonus back when the money is taken out for the wrong reason. Any amount withdrawn from a Lifetime ISA that is not the result of a life event is subject to a 25% withdrawal charge⁹. You can take your savings out without the charge when you are 60 or over, or earlier for the allowed life events such as buying a first home²⁶.

The charge is worked out on the amount you withdraw, not the amount you receive. The official worked example shows the arithmetic: withdrawing £160 means you pay a 25% withdrawal charge of £40 and receive £120 in cash to meet the bill²⁶. If you need a specific sum, you have to withdraw more than the amount you need, to cover both your needs and the 25% charge²⁶.

The charge is deliberately heavier than the bonus it recovers. The FCA's rules describe what the lifetime ISA government withdrawal charge recovers: any lifetime ISA government bonus and any investment growth on that bonus, plus an additional amount²⁷. That "additional amount" is why the effective bite is larger than the bonus alone: a Treasury Committee report characterised access before age 60 as carrying "currently, with a 6.25% penalty"²⁸, measured against the whole pot, while the statutory charge is 25% of the amount withdrawn⁹. Both figures describe the same mechanism from different angles, and the documents present them in those different terms.

Not every movement of money triggers the charge. Withdrawals, removals or losses from a Lifetime ISA do not count for the withdrawal charge if they relate to payments to an invalid account, excess payments, properly levied fees or charges, a default event not attributable to the account investor, or an amount recouped²⁵. Excess contributions paid in by mistake are removed from the account and do not count as a withdrawal⁸. Transfers between Lifetime ISA providers are fine, but transferring money from a Lifetime ISA to a Help to Buy ISA means paying the 25% withdrawal charge, and moving the Lifetime ISA to another type of ISA before age 60 counts as a chargeable withdrawal²⁶.

The full rules, including the charge-free reasons and terminal illness claims, are covered in the Lifetime ISA withdrawal charge and Lifetime ISAs explained.

Junior ISAs and unclaimed Child Trust Funds

A Junior ISA is a tax-free way to save for children up to the age of 18²⁹, available as a cash or a stocks and shares product¹². The account belongs to the child: under the legislation, a junior ISA account is held by the child, who is the beneficial owner of the account investments¹². Money cannot normally be taken out before the child turns 18, with one exception in the rules: withdrawals are permitted where the named child is terminally ill, on a claim accepted by the Board³⁰. When the child turns 18, the Junior ISA automatically turns into an adult ISA¹⁰, and the money becomes theirs to use.

A child cannot have a Child Trust Fund and a Junior ISA of any type at the same time: to move to a Junior ISA, the whole Child Trust Fund amount must be transferred into it³¹. The application to open a Junior ISA must contain a declaration that the child is not an eligible child within the meaning of the Child Trust Funds Act 2004³².

Child Trust Funds matter here because so many are still sitting unclaimed. Over 6 million children have a Child Trust Fund²¹, the government voucher scheme that ran before Junior ISAs. The first accounts began maturing as their holders turned 18, and HMRC's statistics track the flow: around 345,000 accounts matured during the tax year 2023 to 2024 and were claimed or automatically transferred to an ISA³³, around 415,000 matured during the tax year 2025 to 2026³⁴, and in total around 2,958,000 accounts had been claimed or automatically transferred to an ISA as of April 2026³⁴. The Share Foundation manages Child Trust Funds alongside its responsibility for managing the Junior ISA scheme³⁵, including accounts for children in care.

For someone who thinks they have money in a savings account from time in care, the point of contact is the local council³⁶. For everyone else, the route to a lost account is set out step by step in how to find a lost Child Trust Fund, and what the accounts are and how claiming works is covered in Child Trust Funds.

One practical point on rates: Junior ISAs can be variable. NS&I's Junior ISA rate is variable and can change up or down, for example when the Bank of England base rate changes, and NS&I will contact the account holder personally in advance if the rate goes down³⁷.

Moving or combining ISAs without losing the tax benefit

The tax benefit attaches to the money while it stays inside an ISA, so the golden rule of moving money between ISAs is to transfer rather than withdraw and re-deposit. Money in ISAs remains free from UK Income Tax and Capital Gains Tax while you keep it there³, and a proper transfer between providers keeps that treatment continuous. How the process works, and how long it takes, is covered in how to transfer an ISA.

Some ISAs add flexibility on withdrawals. A flexible ISA, which can be a cash or a stocks and shares ISA, allows you to withdraw money and pay it back in again within the same tax year without it affecting your ISA allowance¹⁷. That means a withdrawal from a flexible ISA is not a one-way door: the space it used is restored, provided the money returns before the tax year ends. The rules are covered in flexible ISAs, and the timing pressure of the tax year in the ISA deadline.

Transfers interact with the Lifetime ISA charge in a way worth repeating: transferring a Lifetime ISA to another type of ISA before age 60 counts as a chargeable withdrawal and attracts the 25% charge⁸, while a transfer from a Help to Buy ISA into a Lifetime ISA is allowed without it²⁶. The mechanics of that specific move are in moving a Help to Buy ISA into a Lifetime ISA.

Since 6 April 2024 you can also pay into more than one ISA of the same type in a tax year¹⁶, which makes combining accounts across providers straightforward: you can open as many different adult ISA accounts as you like, as long as you keep within the ISA allowance rules¹⁷. Whether transferring uses your allowance, and whether partial transfers are possible, is covered in does transferring an ISA use my allowance and can I transfer part of my ISA.

Where ISA protection starts and stops

Protection for ISA savers works on two levels: compensation if the provider fails, and redress if the provider treats you badly.

Money held in a cash ISA is a deposit, and deposits with banks and building societies are covered by the Financial Services Compensation Scheme (FSCS)³⁸. The same applies to money held with credit unions, which have their own FSCS deposit protection arrangement³³. Where the compensation rules interact with ISAs there is a specific provision: if the money is held in a Child Trust Fund or Junior ISA account, the compensation will have to be paid into another ISA rather than being cashed, so the tax-free status of the child's money survives the failure³⁸. How the protection works in each situation is set out in how your ISA is protected.

A stocks and shares ISA is different in kind. The money is invested on the stock markets¹¹, so its value moves with those markets, and the FSCS protection that applies to investments covers provider failure, not market falls. Fees also continue to apply while you hold the account, including platform charges, management charges, trading fees and transfer out fees²⁰.

On redress, ISA providers are regulated firms, and the Financial Ombudsman Service handles complaints about individual savings accounts¹¹. The FCA's rulebook also places specific obligations on firms operating Lifetime ISAs, including rules on how the withdrawal charge is described and applied²⁷. If a provider has got something wrong, from a botched transfer to a misapplied charge, the route is the provider's own complaints process first and then the ombudsman, as described in complaining about an ISA provider.

Finally, the tax protection itself has edges. The wrapper shields income and gains while the money stays in ISAs³, but uninvested cash in a stocks and shares ISA is charged to represent basic rate tax²¹, and a Lifetime ISA withdrawal outside the allowed reasons loses part of the bonus and more⁹. The boundaries of the tax break are followed in ISAs and tax: what is tax free and what is not.