What happens to my ISA allowance at the end of the tax year?

Your ISA allowance resets every tax year, and the 2026/27 tax year ends on 05/04/2027. Any part of the £20,000 not used by then is lost and cannot be carried forward.

ISA allowance: £20,000; Total across all your adult ISAs in the tax year. The government has said it will stay at £20,000 until 05/04/2031.; GOV.UK: Individual Savings Accounts (ISAs)
Lifetime ISA limit: £4,000 a year; Counts towards the £20,000 ISA allowance. Open aged 18 to 39; payments allowed until age 50.; GOV.UK: Lifetime ISA
Junior ISA limit: £9,000; Per child, across their cash and stocks and shares Junior ISAs combined.; GOV.UK: Junior Individual Savings Accounts (ISA)
Cash ISA limit from 06/04/2027 (under 65): £12,000; Applies from the 2027/28 tax year to people aged 64 or under at the end of the tax year. People aged 65 or over keep a £20,000 cash ISA limit. The overall ISA allowance stays £20,000. Made law by SI 2026/1018 on 10/09/2026.; legislation.gov.uk: The Individual Savings Account (Amendment) (No. 2) Regulations 2026 (SI 2026/1018)

Tax year 2026/27. Checked 22/09/2026.

The allowance runs with the tax year

Your £20,000 ISA allowance applies to one tax year. The 2026/27 tax year started on 06/04/2026 and ends on 05/04/2027. A fresh allowance starts on 06/04/2027.

HMRC’s rules say anyone who has not paid in up to the limit in a year cannot carry the difference forward. So allowance not used by 05/04/2027 is gone.

Your ISAs themselves do not close at the end of the tax year. Money already in them stays tax-free.

What counts towards the allowance

Only new money paid in (a “subscription”) counts. Interest and investment growth inside the ISA do not count.

Transfers of existing ISA money between providers are not new subscriptions, so they do not use the allowance.
In a non-flexible ISA, taking money out does not give any allowance back.
In a flexible ISA, money taken out can be put back without counting against the allowance, but only in the same tax year as the withdrawal. After 05/04 it would count as a new payment.

When a payment counts as made

HMRC sets out the date a payment counts as paid in, which matters close to 05/04:

Debit or credit card: the date you authorise the payment.
Direct debit: the date the provider is authorised to collect it.
Standing order or bank transfer you send: the date the provider receives the money.
Cheque: the date the provider receives and accepts it, provided it clears.

Provider cut-offs

Providers may set their own earlier cut-off times for payments, transfers or new accounts around the end of the tax year. These are set out in each provider’s terms.

If too much is paid in

Providers cannot see what you pay in elsewhere, so staying within the limit across all providers is your responsibility. If you pay in too much in the current year, the provider can remove the excess and any related gains. For earlier years, HMRC will contact you.

What changes on 06/04/2027

The overall allowance for 2027/28 stays at £20,000, the Lifetime ISA limit at £4,000 and the Junior ISA limit at £9,000; the government has said all three will stay at these levels until 05/04/2031.

From 06/04/2027, people aged 64 or under at the end of the tax year can pay no more than £12,000 a year into cash ISAs (SI 2026/1018, made 10/09/2026). People aged 65 or over keep a £20,000 cash ISA limit. For 2026/27, the full £20,000 can still go into cash ISAs at any age.
From 06/04/2027, transfers from stocks and shares or innovative finance ISAs into cash ISAs are not allowed for people under 65.
From 06/04/2027, any ISA receiving a payment needs a National Insurance number or a declaration that the investor is not eligible for one.

Questions people ask

›When is the ISA deadline for 2026/27?

The tax year ends on 05/04/2027. A payment has to count as made by then to use the 2026/27 allowance; HMRC’s rules on when a payment counts depend on how it is made, for example the date you authorise a card payment or the date the provider receives a bank transfer.

›Can I carry unused ISA allowance into next year?

No. HMRC rules do not allow unused allowance to be carried forward. The new tax year brings a new £20,000 allowance.

›Does moving my ISA to another provider use up my allowance?

No, as long as it is done as an ISA transfer arranged through the new provider. Withdrawing the money and paying it in again counts as a new subscription.

›If I withdraw money from a flexible ISA, can I put it back after 05/04?

Replacing money without it counting against the allowance only works within the same tax year. Money paid back after 05/04/2027 counts towards the 2027/28 allowance.

›Does interest or investment growth count towards the allowance?

No. The allowance limits the money you pay in, not what the ISA earns.

Related guides

Sources

This is information, not advice. Tax treatment depends on your circumstances and can change. For free, impartial guidance, MoneyHelper (backed by the government) can help; for a personal recommendation, speak to a regulated financial adviser.