What is an ISA allowance? A simple guide for 2026/27

What does ISA allowance mean

Your ISA allowance is the total amount you're allowed to pay into ISAs in a single tax year without paying tax on the interest, dividends, or gains that your money earns. It's essentially a yearly limit on how much you can save or invest tax-free.

How much is the ISA allowance for 2026/27

For the tax year that runs from 6th April 2026 to 5th April 2027, the allowance is £20,000. That's unchanged from the year before, and there is nothing to suggest that the £20,000 overall ISA limit is going to fall on 6th April 2027.

However, there is a change to the Cash ISA limit coming into effect on 6th April 2027. You can read about that here.

Can you split your allowance across different ISAs

You can. With Moneybox, your £20,000 can be spread across a Cash ISA, a Stocks & Shares ISA, and a Lifetime ISA, in whatever combination works for you, with the Lifetime ISA capped at £4,000 of that total. You're also allowed to hold more than one ISA of the same type if that suits how you like to organise your money.

What happens if you don't use your full allowance

Unused allowance doesn't roll over into the next tax year. If you pay in £12,000 this year, the remaining £8,000 simply disappears once the tax year ends on 5th April, rather than carrying forward. That's why people often talk about ISA allowances as being ‘use it or lose it’.

Who can open an ISA

Most UK residents aged 18 or over can open an adult ISA. Lifetime ISAs are only available to those between 18 and 39. Junior ISAs work a little differently - they have their own £9,000 allowance, and are opened by a parent or guardian on behalf of a child under 18.

Understanding how your allowance works is really just the starting point. What you actually do with it, whether that's cash, investing, or a mix of both, comes down to your own goals and how comfortable you are with the value of your money moving over time.

ISA and tax rules apply.