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- A Cash ISA is a type of individual savings account that offers tax-free interest
- You can open as many Cash ISAs as you like but can only deposit a maximum of £20,000 across all your ISAs each tax year; however, anyone under the age of 65 will be limited to putting £12,000 into their Cash ISA from April 2027
- Cash ISAs can be opened by any UK resident aged 18 and above
- Cash ISAs are protected by the FSCS
Cash ISAs have been a staple of UK savings for years, offering a straightforward way to earn tax-free interest on your money. But with the allowance set to fall in 2027, it’s worth taking a fresh look at how these accounts work, what they offer, and whether they’re still the right choice for your savings goals.
How does a Cash ISA work?
A Cash ISA is essentially a savings account with a valuable tax advantage.
Think of it as a protective shield around your savings. While your standard savings account might see you paying tax on interest once you’ve exceeded your Personal Savings Allowance, a Cash ISA keeps that interest entirely tax-free regardless of how much you earn.
Example
Say you deposit £10,000 into an easy access Cash ISA offering 4.4% interest. After one year, you’d earn £440 in interest. Because it’s in an ISA, you keep all £440 – no tax deducted.
Compare that with a regular savings account. If you’re a basic rate taxpayer who’s already used your Personal Savings Allowance of £1,000, you’d pay 20% tax on that £440, losing £88 from your wealth. Higher rate taxpayers would lose even more – £176 at 40% tax. The protection against tax offered by a Cash ISA becomes increasingly valuable as your savings grow.
Understanding the Cash ISA allowance
The Cash ISA allowance is part of your overall ISA allowance, which currently stands at £20,000 for the 2026/27 tax year. This means you can deposit up to £20,000 across all your ISAs – whether that’s Cash ISAs, Stocks and shares ISAs, Innovative Finance ISAs, or a combination. Lifetime ISAs also form part of the overall £20,000 allowance, although you can only put up to £4,000 a year into this type of ISA.
There are significant changes coming to Cash ISAs in April 2027. Anyone under 65 will face a cap of £12,000 on paying into a Cash ISA . You’ll still have the full £20,000 annual ISA allowance overall, but only £12,000 of it can go into Cash ISAs. The remaining £8,000 could go into an investment ISA.
For more details on the current rules, check out the ISA rules of 2026/27.
What are the different types of Cash ISA?
Not all Cash ISAs are created equally. Understanding the different types helps you choose the right one for your circumstances.
- Fixed rate Cash ISA
A fixed rate Cash ISA means you get a guaranteed rate of interest for a set term – typically between one and five years. There might be penalties if you take your money out early. - Easy access Cash ISA
An easy access Cash ISA does exactly what it says on the tin – you can withdraw your money whenever you need it without penalties. The interest rate is likely to be variable rather than guaranteed at a specific level.
What are the benefits of a Cash ISA?
- Simplicity: There’s no investment risk with Cash ISAs. Your capital is protected up to £120,000 as part of the FSCS scheme, and you know exactly what rate you’re getting.
- No impact on Personal Savings Allowance: Basic rate taxpayers can earn £1,000 in interest outside ISAs before paying tax, while higher rate taxpayers get £500. Cash ISA interest sits completely outside this system, preserving your allowance for other savings. All your interest inside a Cash ISA is free from tax.
- Flexibility: Cash ISAs offer flexibility in how you structure your savings. You can open multiple Cash ISAs in the same tax year, allowing you to split your money between fixed and easy access accounts as your needs dictate.
Alternatives to a Cash ISA
1. Savings account
One alternative to a Cash ISA is a standard savings account. These have no limit, meaning you can invest more than £20,000 each year, if you have that money available. However, they offer no tax protection, so any interest earned in these accounts above the Personal Savings Allowance is subject to tax.
Head over to AJ Bell's Cash savings hub to see a full list of savings accounts, where we've collected some of the best interest rates in the market. All accounts are protected by the Financial Services Compensation Scheme (FSCS) covering up to £120,000 per bank.
2. Stocks and shares ISA
Another alternative is the Stocks and shares ISA, also called an investment ISA.
This account allows you to invest money for the long term, and with it being an ISA, any gains are protected from the taxman, and yours to keep.
As you’d expect, the £20,000 limit also applies to the AJ Bell Stocks and shares ISA.
Can you transfer a Cash ISA to a Stocks and shares ISA?
Yes, and understanding the transfer rules is important for managing your savings effectively.
Transfer rules for a Cash ISA
You can transfer your Cash ISA to a Stocks and shares ISA without losing the tax-free status of your savings. The crucial thing is to use the ISA transfer process – don’t just withdraw the money and deposit it elsewhere, as that counts as a new contribution against your annual allowance.
Learn more about transferring a Cash ISA to a Stocks and shares ISA
Withdrawing from a Cash ISA
Cash ISA withdrawals depend on the type of account you have. Easy access accounts let you withdraw freely, though you should check the specific terms – some limit the number of withdrawals per year while still being classified as “easy access”.
Fixed rate accounts typically don’t allow withdrawals during the term, and may charge penalties if they do. Always check the terms before opening.
If you withdraw money from a flexible Cash ISA, you can put it back in the same tax year without it counting towards your allowance. Not all Cash ISAs are flexible though, so check before assuming you have this feature.
Cash ISA vs Stocks and shares ISA – which is right for you?
Cash ISAs offer security and guaranteed returns through interest. They’re ideal for emergency funds, short-term savings goals, or if you simply prefer knowing your money is safe and accessible.
Stocks and shares ISAs offer growth potential that can outpace Cash ISAs over longer periods, but your capital is at risk. Markets go down as well as up, and you could get back less than you invest.
Think about your timeline. Need the money within the next few years? Cash ISAs make sense. Saving for 5+ years and comfortable with some risk? Stocks and shares ISAs might offer better long-term growth.
For a detailed comparison, have a look at our guide on Cash ISA vs Stocks and shares ISA.
Want to see how much you could grow your savings in a Stocks and shares ISA?
Use our ISA calculator tool to get a projection.
Frequently asked questions about Cash ISAs
Currently, you can allocate your entire £20,000 annual ISA allowance to Cash ISAs if you wish. That changes from April 2027 when the £12,000 cap kicks in for under-65s, but for now, the full allowance is available.
The maximum you can contribute across all ISA types in the 2026/27 tax year is £20,000. This is a hard limit. If you exceed it, you’ll face penalties and potential loss of tax benefits on the excess amount.
Yes. Although it’s worth remembering that splitting your allowance across multiple accounts doesn’t mean each account gets a £20,000 allowance.
Yes, you can transfer your ISA to another provider if the rate drops. ISA transfer rules allow you to move your current year's ISA as well as previous years' ISAs to a different provider offering better rates. You should initiate the transfer through your new provider rather than withdrawing the money yourself, as this would cause you to lose the ISA's tax-free status.
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More about ISAs
From tips to boost your ISA savings, to understanding which ISA account is best for you, read more about these tax-free accounts.
Open an ISA
Invest up to £20,000 tax free each year with our most popular ISA account. Get started by investing as little as £25 per month.
Transfer an account
Thinking of moving an ISA over to us? It’s easy. We'll just need a few details of your current provider, then we’ll do the rest.
Disclaimer: These articles are for information purposes only and are not a personal recommendation or advice. Tax treatment depends on your individual circumstances and rules may change. ISA rules apply.