How does a Cash ISA work?

What is a Cash ISA? A simple guide to how Cash ISAs work.

On this page: What is a Cash ISA? | Cash ISA allowance | Cash ISA Tax benefits | Who can open a Cash ISA? | Types of Cash ISA | Benefits of a Cash ISA| Is a Cash ISA right for you? | How to open a Cash ISA | FAQs

A Cash ISA is a tax-free savings account available to UK residents, designed to help you grow your savings without paying tax on the interest you earn. 

Tax-free rate is the contractual rate of interest payable where interest is exempt from income tax. Tax treatment and rate of interest payable will depend on individual circumstances and may change in the future.

In this guide, we explain how Cash ISAs work, the current Cash ISA allowance, and the rules you need to know to help you choose the right one.

 

Cash ISA allowance: how much can you save? 

Cash ISAs are one of the most popular savings options in the UK for earning tax-free interest.

You can save up to £20,000 per tax year in a Cash ISA. This is the limit you can invest in ISAs throughout any tax year which runs from 6th April to 5th April.

You can split the £20,000 ISA allowance across different types of ISAs each tax year, meaning any money you invest into a Cash ISA will count towards your overall ISA allowance.

You can open and pay into more than one Cash ISA in the same tax year, as long as you stay within your overall ISA allowance. However, at The Cambridge, you can only pay into one Cash ISA with us each tax year. 

It’s worth noting that under Cash ISA rules, if you don’t invest the maximum into ISAs within any tax year, you can’t carry over the unused amount to the following tax year.

From April 2027, you'll still have a £20,000 ISA allowance, but only £12,000 can be held in a Cash ISA if you're under 65.

 

Cash ISA tax benefits in the UK

The interest earned on a Cash ISA doesn’t count towards your Personal Savings Allowance, meaning you don’t pay any income tax on it. This means you keep every penny of the interest you earn on your Cash ISA.

Types of Cash ISA: Fixed vs Variable explained

There are fixed rate and variable rate Cash ISAs available, both with their own benefits to consider.

Fixed rate Cash ISAs

Pros: A fixed rate Cash ISA offers you an interest rate that won’t change for a set amount of time – giving you a clear indication how much interest your savings will earn over time. Fixed rates often offer a higher interest rate than other Cash ISAs too.

Cons: During the fixed period of time, you likely won’t be able to access your money, and making a withdrawal may incur an interest charge or account closure.

Variable rate Cash ISAs

Pros: Variable rate Cash ISAs offer different levels of access, either allowing you to make as many withdrawals as you need, or specifying a pre-agreed number. Exceeding that number of withdrawals can incur an interest charge, however if you’re looking for flexibility when accessing your money, a variable rate Cash ISA might be for you.

Cons: As the name suggests, the interest rate can go up or down while you hold a variable rate Cash ISA. This can make it difficult to know how much interest your savings will earn over time.

What are the benefits of a Cash ISA?

There’s many benefits to putting your savings into a Cash ISA:

• Savings in a Cash ISA benefit from tax-free interest, meaning you keep every penny earned.
• Cash ISAs allow you to save without affecting your Personal Savings Allowance – which is great if you’ve used it up, or don’t have one.
• Up to £120,000 of your savings are protected by the FSCS.
• There’s a range of options available, so you’re likely to find a Cash ISA to suit your needs.
• You can transfer money from another ISA to a new Cash ISA without affecting your annual ISA allowance. Any money you've already paid in during the current tax year will still count towards your £20,000 limit.

Important notes: 

Don't withdraw the money yourself, as this could affect your ISA's tax free status and use up your allowance. Use the official ISA transfer process instead - your new provider will move the funds for you.

 

Is a Cash ISA right for you?

We understand there’s a lot to consider when deciding if a Cash ISA is right for you.

Here’s some things to consider when deciding:

• Can you lock your money away?
  Cash ISAs often offer a higher interest rate, but your money may be locked away for a set amount of time (usually under 5 years)
• How often will you need access to your money?
  Some Cash ISAs allow unlimited or a set amount of withdrawals, but these can sometimes incur an interest charge.
• Have you used your Personal Savings Allowance?
  Basic rate taxpayer can earn up to £1,000 in interest tax-free outside an ISA. This might reduce the need to open a Cash ISA if you have a small amount of savings.
• Do you want a fixed or variable rate of interest?
  Fixed rates offer certainty, while variable rates can change over time (up or down), so make sure you’ve explored all the options.

Exploring your options can help you find the right fit for your savings goals. 

Need help with Cash ISAs?

Understanding how Cash ISAs work can help you make the most of your tax-free savings each year.

Need a little more support? View all of our ISA guides, call us or pop into branch.