ISA Tax Year End: What Happens to Your Unused Allowance

The ISA tax year runs from 6 April to 5 April, and the current one ends on 5 April 2027. The allowance of £20,000 is a limit for each tax year, and gov.uk describes no way of carrying an unused part of it into the next year. The ISAs you already hold stay open when the year turns over; only the allowance for the new year starts afresh.

The site's rules data was last checked against gov.uk on 26 September 2026. Figures typed in this guide may not yet reflect a later change, and the descriptions of gov.uk pages are summaries that may also lag. The current figures are on the ISA rules at a glance page. General information only, not financial advice.

When does the ISA tax year end?

The ISA tax year begins on 6 April and finishes on 5 April. The current year, 2026-27, ends on 5 April 2027. The gov.uk guide to how ISAs work states the dates in exactly these terms.

This is not the same as the calendar year.

What is the ISA allowance, and is it set for each tax year?

The allowance is the total you can put into ISAs in a tax year. For 2026-27 it is £20,000. gov.uk says you can save up to that amount in one account or split it across several accounts. Our guide to how much you can put in an ISA each year covers the rule in more detail, and how the yearly limit works explains it with examples.

The key point is that the figure belongs to a tax year. gov.uk gives it as the amount you can save in ISAs in a tax year.

What happens to an unused ISA allowance?

gov.uk describes the allowance as something you have every tax year, and its ISA pages do not describe any mechanism for carrying an unused part forward or adding it to a later year. This guide therefore does not assume that an unused part is added to a later year; HMRC or your provider can confirm the position for a particular case. The amount you have already paid in stays where it is.

Two things follow from this:

• gov.uk gives the allowance for each tax year, and the pages read describe no adding of an unused part to a later year.
• Money already inside an ISA is not affected by the year ending. gov.uk states that your ISAs do not close when the tax year finishes, and that you keep your savings on a tax-free basis for as long as you keep the money in your ISA accounts.

Nothing here says whether using or not using the allowance is right for anyone. That depends on personal circumstances, and this guide only sets out how the rule works. To see how a set of payments fits under the limit, the ISA allowance checker shows the arithmetic, and the ISA rules page lists the current figures.

Which payments count towards this year's allowance?

Only money you pay into ISAs during the tax year counts. gov.uk gives the limit as the amount you can save in ISAs in a tax year. The cases below draw on its pages on withdrawing and transferring.

• Payments in. New money paid into any of your adult ISAs counts. The total across all of them is what is measured against £20,000.
• Withdrawals. In an ordinary ISA, taking money out does not free up allowance. In a flexible ISA, the gov.uk page on withdrawing your money says you can take cash out and put it back in the same tax year without reducing that year's allowance. it is worth asking your provider whether yours is flexible.
• Transfers of earlier savings. gov.uk says an ISA transfer can move money saved in this year or in previous years. gov.uk does not say, in the pages read, how a transfer is counted against this year's allowance, so it is worth asking both providers how it will be treated. The next section covers what gov.uk says about using the transfer route rather than withdrawing.

What happens if a payment arrives near the end of the year?

This is where the rules leave room for differences between providers. The tax year ends on 5 April, but the day a payment is counted, and how long it takes to arrive, depends on how the money is sent and on the provider's own processes. gov.uk does not set out cut-off times or processing times for payments, so this guide does not either.

What to check with your provider:

• What is the last day and time for a payment to be counted in this tax year?
• Which counts: the day I send the payment, or the day the provider receives it?
• Does a bank transfer, a debit card payment and a cheque each follow a different timetable?
• What happens to a payment that arrives after the tax year has ended?
• Are the cut-off times different on weekends and bank holidays?

The answers can differ between providers and between payment methods, so the provider's own terms are the source for these points.

Do transfers use up this year's allowance?

The pages read do not say how a transfer is counted against this year's allowance. The gov.uk page on transferring your ISA explains that to move an ISA you contact the provider you want to move to and complete a transfer form. It also warns that if you withdraw the money yourself rather than transferring it, you will not be able to put that part of your tax-free allowance back in again.

In short:

• gov.uk says to contact the provider you want to move to and complete a transfer form, rather than withdrawing the money yourself.
• gov.uk says the money moved can have been saved this year or in previous years. How money saved this year is treated in the move is worth confirming with both providers.
• A withdrawal followed by a new payment is a different thing from a transfer, and it can use up allowance.

A transfer is a process rather than a single instant, and it takes time (gov.uk gives 15 working days for transfers between cash ISAs and 30 calendar days for other types of transfer), so it can straddle the end of a tax year. Whether that matters in a given case is worth asking the providers involved. Our fixed-rate ISA switch calculator covers the cost side of a move, not the rules.

Do the Lifetime ISA and Junior ISA have their own limits?

Yes, each has its own yearly limit, and they work differently.

• Lifetime ISA. gov.uk says you can pay into only one Lifetime ISA in a tax year, and the most you can pay in is £4,000. That amount sits inside the overall £20,000, not on top of it. Payments into a Lifetime ISA therefore use up part of the same overall allowance. gov.uk describes a bonus of 25% on what you save, up to a maximum of £1,000 a year.
• Junior ISA. For a child's account the yearly limit is £9,000. gov.uk gives this as a separate figure on its Junior ISA page. The adult allowance is not described there as being reduced by payments into a child's account, but the two pages are separate sources, so the Junior ISA page is the place to check the position for a particular family.

Both limits are per tax year, in the same way as the main allowance, and both are read from the site's rules data.

How does the allowance split between a Cash ISA and a Stocks and Shares ISA?

The split is plain arithmetic. This example uses assumed amounts chosen only to show the sums; they are not rule figures and not suggestions.

Suppose someone pays £6,000 into a Cash ISA during the tax year and £8,000 into a Stocks and Shares ISA in the same year.

The total counted against the allowance is £6,000 plus £8,000, which is £14,000. The amount remaining in that year is £20,000 minus £14,000. That remainder is the unused part. gov.uk describes no carry forward of an unused part.

Two more things about the same example:

• If the person had put all £14,000 in one account, the total counted would be the same. The allowance is measured across accounts, not per account.
• Money in a Stocks and Shares ISA can go down as well as up, so its value at any point may differ from the amount paid in. The allowance counts what was paid in, not what the account is worth.

To try other splits, the ISA allowance checker lets you enter your own amounts.

What to check with your provider

• How does the provider count the payment date around 5 April?
• Is my ISA flexible, so that cash I take out can be paid back in during the same year?
• If I moved money from another ISA, was it treated as a transfer?
• How many payments into different accounts have I made so far this tax year?
• Do any of my accounts have their own minimums, limits or processing times?

Frequently asked questions

When does the ISA tax year end?

It ends on 5 April. The current tax year, 2026-27, ends on 5 April 2027, and the next one starts on 6 April.

Does an unused ISA allowance carry over?

gov.uk sets the allowance for each tax year and describes no carry forward, so this guide does not assume an unused part is added to a later year. The allowance for a new tax year is the figure gov.uk gives for that year, currently £20,000.

Does transferring an old ISA use this year's allowance?

The pages read do not say how a transfer is counted against this year's allowance. gov.uk says to use the transfer form with the new provider, because if you withdraw the money yourself you will not be able to reinvest that part of your tax-free allowance again. Ask both providers how a particular transfer is treated.

Is the Lifetime ISA limit extra to the main allowance?

No. The Lifetime ISA limit of £4,000 a year sits within the overall £20,000. The Junior ISA has its own separate yearly limit of £9,000.

What time is the cut-off for paying into an ISA before the year ends?

gov.uk does not set a cut-off time, and it can vary by provider and by payment method. The provider is the place to ask.

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This guide does not constitute financial advice. Your personal situation, tax position, and savings goals may mean different strategies are appropriate. Consider speaking to a regulated financial adviser if you are uncertain.