Flexible cash ISAs explained

What is your ISA allowance?

Each year the government sets a maximum amount you can save into ISAs.

For the 2026/2027 tax year, the ISA allowance is £20,000. And your allowance resets every tax year (the tax year ends on April 5).

Your ISA allowance applies to all your ISAs combined. Which means you can spread your allowance across different ISAs each tax year.

From April 6 2027, the overall ISA allowance stays at £20,000. But if you're younger than 65, you'll only be able to put up to £12,000 of your allowance into a cash ISA. 

To find out more about these changes, you can read our guide to cash ISA rule changes. 

How ISA allowances work

Your annual ISA allowance applies across all the ISAs you pay into during a single tax year.

You can pay into multiple different ISAs in a tax year. But the total amount you contribute can't exceed your annual allowance.

You could put your full allowance into one ISA. Just remember the cash ISA limits for under 65s mentioned above. Or choose to split your allowance across different types of ISA. The choice is yours.

You can only pay into one Principality cash ISA each tax year.

What is a flexible cash ISA?

Not all ISAs let you make withdrawals, but some do. A flexible ISA lets you take money out and lets you replace that money in the same tax year without using your ISA allowance.

If you think you might need access to your savings, you should take time to understand how flexible ISAs work.

Let's look at an example. For this example, we'll assume you have a cash ISA allowance of £20,000.

Step 1: You pay £10,000 into your flexible cash ISA.
Step 2: Later you withdraw £2,000.
Step 3: Later that same tax year, you replace that £2,000 into the same flexible cash ISA.

Because your ISA is flexible, you still have £10,000 ISA allowance remaining.

Even though you've technically paid in £12,000 in total, the £2,000 you withdrew is considered as a 'replacement' rather than you using up your allowance.

Why might you choose a flexible cash ISA?

A flexible cash ISA may suit you if you:
•    Occasionally need access to your savings. 
•    Want the flexibility to replace money you’ve withdrawn without affecting your annual ISA allowance. 
•    Plan to use an ISA for emergency savings you may need to withdraw. 

Remember:

•    Not every cash ISA is flexible.
•    You must replace any money in the same tax year you made the withdrawal
•    Rules vary between providers, so it’s always worth checking your account’s terms and conditions.