ISA rules
Flexible ISA: putting back what you took out
Enter what you have paid in this tax year, what you have taken out, and whether the account is flexible. The tool shows how much you can still pay in, and the figure for the other kind of account.
Room left after taking money out
You can still pay in
£13,000
| Allowance not yet used | £10,000 |
| Withdrawals you can put back | £3,000 |
| If it were not flexible | £10,000 |
Money taken out must go back before 5 April of the same tax year to keep this room.
A flexible ISA is one whose terms allow you to withdraw cash and replace it later in the same tax year without the replacement counting as a new subscription. Any ISA lets you take money out at any time without losing the tax benefit on what remains, but only a flexible one gives back the allowance used by the money withdrawn. GOV.UK gives the standard example: with the £20,000 allowance, you pay in £10,000 and take out £3,000. If the ISA is flexible you can still pay in £13,000; if it is not, only £10,000, because the £3,000 withdrawn has used allowance for good. The money must be put back before 5 April of the same tax year; after that date the room is lost. Flexibility is an option for the provider, not a right, and from 6 April 2027 money replaced in a cash ISA may not take a saver past the cash ISA ceiling.
Sums checked by Radif Partners · Editorial policy · How the sums are done
The rule in the regulations
Flexibility comes from regulation 5DDB of the ISA Regulations 1998. It lets the terms of an ISA provide for cash withdrawn to be replaced, in whole or in part, without affecting the saver’s subscription limit. GOV.UK sums it up as being able to take cash out and put it back in the same tax year without reducing the current year’s allowance. The word that matters is cash: the rule concerns money withdrawn from the account, so it fits naturally with cash ISAs and with the cash part of other ISAs that offer it.
Five withdrawals compared
| Paid in this year | Taken out | Room left if flexible | Room left if not | Difference |
|---|---|---|---|---|
| £10,000 | £3,000 | £13,000 | £10,000 | £3,000 |
| £20,000 | £5,000 | £5,000 | £0 | £5,000 |
| £20,000 | £20,000 | £20,000 | £0 | £20,000 |
| £15,000 | £2,000 | £7,000 | £5,000 | £2,000 |
| £6,000 | £6,000 | £20,000 | £14,000 | £6,000 |
The third line is the extreme case. A saver who has paid the whole £20,000 and then takes all of it out has the full allowance back if the account is flexible, and nothing at all if it is not. In the last line, £6,000 paid in and fully withdrawn leaves £20,000 of room with flexibility against £14,000 without it. The difference column is always the amount withdrawn, capped at what was paid in.
Same tax year, and what that means in practice
The window for putting money back closes on 5 April. A withdrawal on 1 April leaves five days. There is no carry-over: if the money returns on 6 April, it uses the new year’s allowance like any other deposit. For an under-65 saver crossing into 2027/28, that new allowance carries the £12,000 cash ceiling of SI 2026/1018.
The replacement is governed by the terms of the account the money came from. Moving an ISA between providers without losing its status is a different process, done by a transfer through the new provider.
The cash ceiling from April 2027
The amending regulations change regulation 5DDB so that replacing money in a cash ISA may not exceed the cash subscription limit. Take an under-65 saver who pays £12,000 into a flexible cash ISA in 2027/28, withdraws £4,000 and then wants to put it back. Under the old logic, the £4,000 replacement would not count at all. The amended rule ties the replacement to the cash limit, so the saver can only rely on what the regulations allow within the £12,000. Detailed guidance for providers is still to be published; the page on the April 2027 changes keeps track of what is known.
Where flexibility does not reach
Lifetime ISAs have their own withdrawal rules, with a 25 % charge when money is taken out for a purpose other than a first home, reaching 60 or terminal illness. Money in a Junior ISA is locked until the child is 18. And whatever the account, flexibility only restores allowance: it does not undo the fact that money outside the ISA earns interest that enters your tax calculation. The ISA allowance page shows the whole year’s position, and the main calculator the tax on savings held outside.