ISA vs savings account: the differences explained

What is an ISA?

An ISA (Individual Savings Account) is a tax-free wrapper for savings and investments. Any interest, dividends, or capital gains generated within an ISA are entirely free from UK income tax and CGT — permanently, not just while you are within an annual allowance.

There are four main types of ISA available to UK adults:

• Cash ISA — holds cash and pays interest, like a savings account but tax-free
• Stocks and shares ISA — holds investments including shares, funds, ETFs and investment trusts; gains and income are tax-free
• Lifetime ISA — available to those aged 18-39, for first home purchase or retirement; government adds a 25% bonus on contributions up to £4,000 per year
• Innovative Finance ISA — holds peer-to-peer loans; higher risk, limited protection

The annual ISA allowance for 2025/26 and 2026/27 is £20,000 per individual. This can be split across multiple ISA types in the same tax year. Unused allowance cannot be carried forward.

What is a savings account?

A savings account is a bank or building society deposit account that pays interest on your balance. The key difference from an ISA is that interest earned in a savings account is potentially subject to income tax above your Personal Savings Allowance (PSA):

• Basic rate taxpayers can earn up to £1,000 in interest tax-free per year
• Higher rate taxpayers can earn up to £500 in interest tax-free per year
• Additional rate taxpayers have no PSA — all interest is potentially taxable

At current rates, a basic rate taxpayer with more than approximately £21,000 in savings earning 4.75% AER would exceed the £1,000 PSA and start paying tax on interest. A higher rate taxpayer would exceed the £500 PSA with just over £10,500 in savings at the same rate.

As of June 2026, the Bank of England base rate is 3.75%, held on 29 April 2026. The best easy-access savings accounts pay approximately 4.75-5.00% AER, and the best one- to two-year fixed rate accounts reach approximately 4.65-4.75% AER.

ISA vs savings account: key differences

When a savings account beats an ISA

For basic rate taxpayers with modest balances, a regular savings account can match or beat a cash ISA — particularly if the savings account pays a higher headline rate.

If your total savings balance is low enough that the interest earned stays within your PSA, the tax-free benefit of an ISA is irrelevant. In that case, simply choosing the highest-paying account — ISA or not — is the right decision.

For example: a basic rate taxpayer with £15,000 earning 4.75% generates approximately £712 in annual interest — below the £1,000 PSA. If the best savings account pays 5.00% and the best cash ISA pays 4.75%, the savings account wins.

When an ISA beats a savings account

The ISA advantage grows with your balance, your income tax band, and the passage of time.

Higher rate taxpayers exhaust their £500 PSA at just over £10,500 in savings at current rates. Above that, every pound of interest from a savings account is taxed at 40%. A cash ISA paying the same rate as a savings account is worth meaningfully more to a higher rate taxpayer.

The compounding advantage of the ISA also matters over time. Money saved in an ISA stays sheltered permanently — the tax protection does not expire and does not depend on your income level in future years. Approximately 4.8 million consumers are forecast to become higher rate taxpayers between 2022/23 and 2030/31 due to frozen tax thresholds. Many of these savers will find their PSA halved from £1,000 to £500, materially changing the calculus in favour of ISAs.

The April 2027 ISA rule changes

A significant rule change is coming from April 2027 that affects this comparison directly. Under current plans, the cash element of the ISA allowance will reduce from £20,000 to £12,000 per year for under-65s. Those wanting to use the full £20,000 annual ISA allowance will need to invest at least £8,000 in a stocks and shares ISA.

This change has two implications. First, it makes maxing the full ISA allowance conditional on investing rather than purely saving cash. Second, it increases the relative attractiveness of starting a stocks and shares ISA now — building an invested ISA pot before the rules change means more of your allowance can be used flexibly going forward.

Stocks and shares ISA vs cash savings

For investors with a time horizon of five years or more, the comparison should not simply be between a cash ISA and a savings account — it should include a stocks and shares ISA.

Equity markets have historically returned approximately 7-10% per year over long periods, significantly outpacing savings rates even at today's elevated levels. A stocks and shares ISA compounds that return entirely free of tax on gains and dividends.

The trade-off is risk. Unlike a savings account or cash ISA — where your capital is secure up to FSCS limits — investments in a stocks and shares ISA can fall in value. For money you may need within one to two years, cash savings remain more appropriate. For money you will not need for five years or more, a stocks and shares ISA with a diversified investment approach has historically offered meaningfully better long-term outcomes.

How to choose with us

With us, you can open a stocks and shares ISA to invest in shares, funds, and ETFs within a tax-free wrapper, with the full £20,000 annual allowance available. Our ISA has no annual account fee and offers access to over 11,000 global shares and funds.

For a full comparison of ISA types, see our guide on understanding your ISA allowance. For guidance on how shares are taxed outside of an ISA, see how are shares taxed in the UK. For the longer-term growth case for investing, see our guide on how to invest in shares.

Past performance is not a reliable indicator of future results. The value of investments can fall as well as rise and you may get back less than you invest.