Cash ISA vs ordinary savings: which suits your tax position?

A Cash ISA and an ordinary savings account work in much the same way: you pay money in, it earns interest, and you take it out when you need it. The difference is tax. Interest from an ordinary savings account counts towards your Personal Savings Allowance, and anything above that allowance is charged at your usual rate of income tax, which is 20%, 40% or 45%¹. Interest inside a Cash ISA is tax-free and does not count towards that allowance at all³.

That difference has a cash value. The gap between a one-year fixed cash ISA and a savings account was £121, and the top instant-access cash ISA could yield £152 more interest after a year than the market-leading savings account for a higher-rate taxpayer with £20,000, assuming the variable rate stayed the same⁵. Those figures come from a comparison taken on 13 November 2025 and depend on the rates available at the time.

For the 2026/27 tax year, under-65s can pay up to £20,000 into a Cash ISA⁶. From 6 April 2027 that falls to £12,000 for under-65s, while savers aged 65 and over keep the £20,000 Cash ISA allowance³. The overall ISA limit stays at £20,000⁷.

Cash ISA or ordinary savings: the difference is tax on interest

Both accounts pay interest. The tax treatment is what separates them. A Cash ISA works like a normal savings account, but you do not pay income tax on the interest you earn⁸. A standard savings account does not have that protection: if your money sits in one rather than an ISA, you may have to pay tax on the interest¹⁰.

The practical effect is that a Cash ISA shelters your interest from tax entirely, while an ordinary account exposes it once it passes your allowance. A fixed rate Cash ISA is tax-free and does not count towards your Personal Savings Allowance, which is the key difference from a fixed rate bond¹¹.

That does not automatically make a Cash ISA the better home for your money. An ordinary savings account may pay a higher rate before tax, and for some savers the tax bill on the interest is small enough that the headline rate still wins. The comparison depends on your tax band, how much you hold and the rates on offer. The £121 and £152 figures above show the gap can be modest even for a higher-rate taxpayer, and it moves as rates change⁵.

Where a Cash ISA tends to matter more is for larger balances, for higher and additional rate taxpayers, and for anyone whose interest is close to or above their allowance. It also matters for anyone who wants certainty: the tax-free status does not depend on the rate you happen to be earning that year.

How interest on ordinary savings is taxed

Interest from an ordinary savings account is taxable once it exceeds your Personal Savings Allowance. Any interest above the allowance is charged at your standard income tax rate, whether that is 20%, 40% or 45%¹². The same rates apply to savings interest generally: 20%, 40% or 45%¹.

The allowance itself is a fixed amount of savings interest you can receive tax-free each year. Savings held in tax-free accounts such as ISAs do not count towards it¹³. So the allowance is not a separate pot that sits alongside your ISA; it applies only to interest from taxable accounts.

A few practical points follow from this:

• Interest is taxed in the year it is paid or credited, not the year you opened the account.
• Your allowance depends on your highest rate of income tax, so a change in earnings or in the tax you pay can change how much interest is tax-free.
• If you hold savings in a Stocks and Shares ISA, interest on uninvested cash held there is treated differently from interest in a Cash ISA, and a flat rate charge representing tax at basic rate can apply¹⁴.

For most basic rate taxpayers with modest savings, the allowance covers the interest and no tax is due. For higher rate taxpayers, and for anyone with a large balance, the allowance runs out sooner and the tax charge becomes real. That is the point at which the tax-free wrapper of a Cash ISA starts to earn its keep.

Cash ISA interest is tax-free and sits outside the Personal Savings Allowance

Interest paid inside a Cash ISA is tax-free, and it does not count towards your Personal Savings Allowance³. The Personal Savings Allowance does not apply to any growth or interest paid in an ISA³. Interest you earn in a cash ISA also does not count towards your ISA allowance, so it does not reduce how much you can pay in¹⁵.

This matters most if you hold money in both a Cash ISA and an ordinary account. Because ISA interest stays outside the allowance, your full Personal Savings Allowance remains available for the interest on your ordinary savings⁸. If you moved that money out of the ISA and into a taxable account, the interest would start eating into the allowance instead.

The interest you earn on ISAs and other tax-free accounts is not taxable, so it will not use up any of your Personal Savings Allowance¹⁶. Cash ISAs are tax-free, meaning you do not have to declare any interest earned¹⁷. A Cash ISA is like a normal savings account, but you do not have to pay any income tax on the interest you earn¹⁸.

Which suits your tax position

The right choice depends on your tax band, how much interest you expect, and whether you are likely to need the money. The table below sets out how the two compare on the points that decide it.

For a basic rate taxpayer whose interest stays within the allowance, an ordinary account can be simpler and may pay more. For a higher or additional rate taxpayer, or anyone with a balance large enough that the interest exceeds the allowance, the tax-free wrapper of a Cash ISA removes a charge that would otherwise apply¹.

Official statistics give a sense of who holds ISAs and how much. Individuals with an income of £150,000 or more had average ISA holdings of £94,894 in the 2022 to 2023 tax year, and the 65 and over age group had the highest average ISA market value at £64,386, compared with £8,288 for under-25s²¹. Those figures describe existing holdings, not what any individual should do.

If you are unsure which side of the allowance you fall on, the personal savings allowance page explains how it is worked out, and how tax on savings interest works covers the mechanics.

Easy access or fixed: how Cash ISA access works

Cash ISAs come in two main forms: instant access and fixed rate²⁰. An easy access Cash ISA gives you more access to your money, but the interest rate can go up or down⁸. It suits short-term savings, emergency funds or money you may need at short notice²². A fixed rate Cash ISA locks your money away for a set term in return for a rate that is fixed for that period.

The access rules differ sharply between the two:

• Easy access: you can add or take out money when you need to, and the rate can move⁸.
• Fixed rate: you usually cannot withdraw money during the fixed term without a penalty, unless the product rules allow it²³.

A Cash ISA is a savings account with tax-free interest, and the access terms are set by the product you choose²⁴. If you need the money back before a fixed term ends, check the terms first: the penalty can reduce or wipe out the interest you have earned.

Cash ISA allowance for under-65s to fall to £12,000

The Cash ISA allowance for under-65s is set to fall from £20,000 to £12,000 from 6 April 2027³. The change was announced in the 2025 Budget, which introduced a cash limit of £12,000 within the overall annual ISA limit of £20,000²⁵. The overall annual ISA limit stays at £20,000, so the remaining £8,000 can go into a Stocks and Shares ISA or another permitted ISA type⁷.

The reduction applies to new deposits only. It will only apply to new deposits you make from April 2027 and will not have any impact on savings you have already built up⁶. Existing Cash ISA savings are unaffected by the change.

The measure amends the Individual Savings Account Regulations 1998 to reduce the annual cash ISA subscription limit to £12,000 for individuals aged under 65 from 6 April 2027²⁶. The Individual Savings Account (Amendment) Regulations 2026 set the annual Cash ISA subscription limit for investors below the age of 65 at £12,000 from 6 April 2027²⁸.

What changes for savers aged 65 and over

Savers aged 65 and over are unaffected by the reduction. Their Cash ISA allowance remains at £20,000 for the 2027/28 tax year⁶. Savers over the age of 65 will continue to be able to save up to £20,000 in a cash ISA each year²⁹. For investors aged 65 or over, the annual Cash ISA limit will remain at £20,000⁷.

Entitlement to the higher limit applies from the start of the tax year in which an individual turns 65³. So you do not have to wait until your birthday falls in that tax year; the higher allowance applies from the start of it.

The government retained the £20,000 limit for this group in recognition of the need of those approaching retirement to restructure and derisk their investments, with transfers into Cash ISAs allowed for this group⁷. That connects to a second change: from 6 April 2027, transfers from a Stocks and Shares ISA or an Innovative Finance ISA into a Cash ISA are prohibited where the account holder is under 65⁷. For those aged 65 and over, the transfer restriction is disapplied from the start of the tax year in which they turn 65³.

Individuals aged 65 or older are estimated to be overrepresented among cash ISA subscribers, at 34% of the population subscribing to a cash ISA compared with 24% of the UK adult population. Those aged 55 to 64 are also overrepresented, at 18% compared with 17%²⁶.

What happens when a fixed rate Cash ISA matures

When a fixed rate Cash ISA reaches the end of its term, your savings are unlocked. You can usually add to your savings, take money out, transfer to another ISA or close your account¹¹. What happens by default depends on the provider, and the differences matter because a default rollover can leave your money on a rate you did not choose.

The common outcomes are:

• Convert to a variable rate Cash ISA. After the fixed rate period, the account becomes a variable rate Cash ISA³⁰.
• Convert to an instant access Cash ISA. The account matures into an instant access Cash ISA at the end of the fixed term, earning the provider's standard variable rate³¹.
• Convert to a named saver account. After the fixed term ends, the account changes to an ISA Saver³².
• Automatically transfer into a new fixed term. At maturity, the account automatically transfers into a new one-year fixed rate Cash ISA unless the customer says otherwise⁹.
• Convert to a loyalty account. If you choose not to reinvest, the account automatically converts to a Loyalty Cash ISA³³.

Interest due at maturity is paid to you, and it does not count towards your ISA allowance³³. That means the interest you receive does not reduce how much you can pay in during the year.

The practical step is to diarise the maturity date and check the terms before it arrives. If the default is a new fixed term, you may need to act to avoid being locked in again. If the default is a variable rate, the rate may be lower than what you could get elsewhere. The fixed-rate maturity page covers the options in more detail.

Will I still be able to transfer a Stocks and Shares ISA into a Cash ISA?

Under the current rules, funds invested in a Stocks and Shares ISA can only be transferred to another Stocks and Shares ISA, while funds invested in a Cash ISA can be transferred to a Stocks and Shares ISA or another Cash ISA³⁴. In practice, providers have allowed Stocks and Shares ISA to Cash ISA transfers, and some still advertise the option³⁵.

That changes from 6 April 2027. Transfers from a Stocks and Shares ISA or an Innovative Finance ISA to a Cash ISA are prohibited where the account holder is below the age of 65⁷. For those aged 65 and over, the transfer restriction is disapplied from the start of the tax year in which they turn 65³. Independent guidance confirms that from April 2027 you cannot transfer a Stocks and Shares ISA into a Cash ISA³⁷.

Other transfers are unaffected. Cash ISA to Cash ISA transfers remain available, as do Cash ISA to Stocks and Shares ISA transfers³⁶. A Cash ISA or Stocks and Shares ISA can be transferred into any other type of ISA except Junior ISAs³⁸. If you transfer money from a Cash ISA into a Stocks and Shares ISA in the same tax year, the amount you transferred still counts as used allowance: paying £1,000 into a cash ISA and then transferring it to a stocks and shares ISA in the same year would still have used up £1,000 of that year's ISA allowance³⁹.

If you are considering a transfer, the ISA transfers section covers the process and the Stocks and Shares ISA transfers page explains how in-specie and cash transfers differ.

Is it worth having a Cash ISA if you pay no tax on your savings interest?

It can still be worth holding one, even if your interest currently stays within your Personal Savings Allowance. The interest inside a Cash ISA is tax-free and does not use up your allowance, so it keeps that allowance free for interest from other savings³. If your balance grows, or your tax position changes, the ISA wrapper means you do not have to move money later to avoid a tax charge.

There is also the question of rate. An ordinary account may pay more before tax, and for a saver whose interest is well within the allowance, the tax-free wrapper may not be worth a lower rate. The £121 and £152 figures show the gap can be small even for a higher-rate taxpayer, so the rate on offer matters as much as the tax treatment⁵.

A Cash ISA is a savings account with tax-free interest, and it works similarly to other savings accounts but allows eligible savers to earn interest tax-free, subject to annual ISA subscription limits and current tax rules⁴⁰. Whether it suits you depends on your rate, your balance and how likely you are to need the money.

If you are weighing up where to hold your savings, the savings accounts guide sets out the account types, and easy access vs fixed-rate savings compares the access trade-off. For help with tax on savings, MoneyHelper offers free, impartial guidance.