Flexible ISAs: What they are and how they work

Before opening an ISA, it’s worth checking whether it’s flexible to make sure it’s the right account for you.

An ISA is a tax-efficient way to save money. Each tax year, you're given an annual ISA allowance (or a limit to the amount you can pay into an ISA). For the 2024/2025 tax year, this stands at £20,000. When comparing ISA accounts, you might notice that some are termed "flexible". This guide explains what flexible ISAs mean and why they can be useful.

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The Financial Services Compensation Scheme (FSCS) guarantees that it will step in to compensate the first £85,000 (£170,000 for a joint account) you have saved with a UK-authorised bank, building society or credit union in the event that the business goes bust.

Best flexible cash ISA rates

Table: sorted by interest rate, promoted deals first
1 - 10 of 136
Name Product Interest rate Minimum investment Interest paid Withdrawals Deposit protection Open via Incentive Table product description Apply link
Chip – Chip Cash ISA (powered by ClearBank)
5.1% AER variable
£1
Monthly
Instant access
FSCS logo
protected
Open via: mobile app
Go to site
View details
Aldermore – 30 Day Notice Cash ISA Issue 12
4.5% AER variable
£1,000
Anniversary of account opening
30 days notice needed (charge applies )
FSCS logo
protected
Open via: website
Go to site
View details
Aldermore – 30 Day Notice Cash ISA Issue 12
4.5% AER variable
£1,000
Monthly
30 days notice needed (charge applies )
FSCS logo
protected
Open via: website
Go to site
View details
Aldermore – Easy Access Cash ISA Issue 1
4.25% AER variable
£1,000
Anniversary of account opening
Instant access
FSCS logo
protected
Open via: website
Go to site
View details
Aldermore – Easy Access Cash ISA Issue 1
4.25% AER variable
£1,000
Monthly
Instant access
FSCS logo
protected
Open via: website
Go to site
View details
Zopa – Smart ISA - Access ISA pot
5.08% AER variable (includes a 0.5% bonus )
£1
Monthly
Instant access
FSCS logo
protected
Open via: mobile app
Go to site
View details
Progressive Building Society – 1 Year Double Access Cash ISA Account (Issue 3)
Progressive BS – 1 Year Double Access Cash ISA Account (Issue 3)
5.05% AER variable
£500
Yearly
Instant access
FSCS logo
protected
Open via: branch, post
Go to site
View details
Principality BS – Online Bonus 5 Access Cash ISA
5% AER variable (includes a 1.45% bonus )
£1
Yearly
Instant access
FSCS logo
protected
Open via: website
Go to site
View details
Newcastle BS – Newcastle Single Access ISA (Issue 1)
5% AER variable
£1
Anniversary of account opening
Instant access
FSCS logo
protected
Open via: branch, website
Go to site
View details
Paragon Bank – Double Access Cash ISA - Issue 4
4.95% AER variable
£1,000
Monthly
Instant access
FSCS logo
protected
Open via: website
Go to site
View details
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What is a flexible ISA?

A flexible ISA is an ISA that lets you withdraw funds and pay them back into your ISA account in the same tax year, without affecting your annual ISA allowance. This can apply to cash ISAs, stocks and shares ISAs and innovative finance ISAs, but not all providers offer flexible ISAs so you’ll need to check.

A flexible ISA means you won’t be penalised if you access some of your ISA funds.

How does a flexible ISA work?

Let’s say you’ve paid £20,000 into a flexible cash ISA, using your full ISA allowance for that year. In the same tax year, you decide to withdraw £10,000. Because the ISA is flexible, the withdrawal doesn’t affect your annual allowance and you can repay the £10,000 before the end of the tax year.

Note that you must repay it into the same ISA account you took it out of, although you can withdraw from a flexible cash ISA and replace it in a flexible stocks and shares or innovative finance ISA instead.

By contrast, if the ISA was not flexible and you’d paid in £20,000 but withdrawn £10,000, you wouldn’t be able to repay the £10,000 as this would mean you’d have exceeded your annual allowance.

Do I need a flexible ISA?

Ultimately, whether you need a flexible ISA is up to you. But if you think you could get close to using up your £20,000 annual ISA allowance and you plan to make withdrawals, it’s well worth choosing a flexible ISA.

On the other hand, if you know you won’t get close to reaching your annual ISA limit or you don’t plan to make any withdrawals, choosing a flexible ISA won’t be so important.

Pros and cons of flexible ISAs

Pros

  • Enables you to withdraw funds and replace them within the same tax year without impacting your annual ISA allowance
  • You can also withdraw funds from a cash ISA and replace them in a flexible stocks and shares or innovative finance ISA
  • Good option if you need to access funds in an emergency

Cons

  • Not all ISAs are flexible
  • Flexible ISAs might not necessarily offer the best rates
  • You must repay the funds into the same ISA account (unless you choose a different type of ISA)

Bottom line

Choosing a flexible ISA could be a great option if you’re worried that you will get close to using your full ISA allowance and might need to make some withdrawals. Just remember that not all providers offer flexible ISAs and it’s important to check how competitive the account is before making a decision.

Frequently asked questions

We show offers we can track - that's not every product on the market...yet. Unless we've said otherwise, products are in no particular order. The terms "best", "top", "cheap" (and variations of these) aren't ratings, though we always explain what's great about a product when we highlight it. This is subject to our terms of use. When you make major financial decisions, consider getting independent financial advice. Always consider your own circumstances when you compare products so you get what's right for you. Most of the data in Finder's comparison tables has the source: Moneyfacts Group PLC. In other cases, Finder has sourced data directly from providers.
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Writer

Rachel Wait is a freelance journalist and has been writing about personal finance for more than a decade, covering everything from insurance to mortgages. She has written for a range of personal finance websites and national newspapers, including The Observer, The Mail on Sunday, The Sun and the Evening Standard. Rachel is a keen baker in her spare time. See full bio

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