Cash ISA vs Easy-Access Savings: Which Pays More After Tax in 2026/27?

Last updated: 12 September 2026

A Cash ISA is not automatically better than an ordinary easy-access savings account. The real comparison is the interest rate you can get, how much of your savings interest is taxable, how quickly you need the money and whether preserving ISA allowance matters to you.

Cash ISA vs easy-access savings: the core difference

For the 2026/27 tax year, you can subscribe up to £20,000 across your ISAs. Interest earned on cash inside an ISA is not subject to UK Income Tax and does not need to be declared on a tax return. Outside an ISA, savings interest can still be tax-free if it falls within your available allowances.

The Personal Savings Allowance is what changes the maths

For 2026/27, the Personal Savings Allowance (PSA) is:

• £1,000 for a basic-rate taxpayer;
• £500 for a higher-rate taxpayer;
• £0 for an additional-rate taxpayer.

Your tax band for this purpose takes your savings interest into account, so someone close to the higher-rate threshold should not simply assume they have a £1,000 allowance. HMRC also has a separate starting rate for savings of up to £5,000 for people with sufficiently low other income. If your other income is £17,570 or more, you are not eligible for that starting-rate band.

Worked example: when the ordinary savings account wins

To show the tax effect without pretending that today’s market-leading rates will stay the same, use an illustrative comparison:

• ordinary easy-access savings: 4.50% AER;
• easy-access Cash ISA: 4.20% AER.

These are example rates for the calculation, not product recommendations.

A basic-rate taxpayer with £25,000 in the ordinary account would earn £1,125 gross interest over a full year. The first £1,000 is covered by the PSA. The remaining £125 would be taxed at 20%, producing £25 of tax and £1,100 net interest.

The same £25,000 at 4.20% inside the Cash ISA would produce £1,050 tax-free interest.

In that example, the taxable account still wins by £50 because its higher AER is enough to compensate for the small amount of tax.

Worked example: when the Cash ISA overtakes it

Keep the same illustrative rates but increase the balance to £50,000.

At 4.50%, the ordinary savings account produces £2,250 gross interest. For a basic-rate taxpayer, £1,000 is covered by the PSA and £1,250 is taxable at 20%. That creates £250 of tax, leaving £2,000 net interest.

At 4.20%, the Cash ISA produces £2,100 tax-free.

Now the Cash ISA is ahead by £100 despite having the lower headline rate.

Higher-rate taxpayers hit the tax point sooner

Using the same £25,000 balance and 4.50% ordinary-savings rate, the gross interest is £1,125. A higher-rate taxpayer has a £500 PSA, so £625 would be taxable at 40% in 2026/27. That leaves £875 net interest.

The 4.20% Cash ISA still produces £1,050, so in this example the ISA is ahead by £175.

An additional-rate taxpayer has no Personal Savings Allowance. At a 45% savings tax rate in 2026/27, £1,125 gross interest would fall to £618.75 after tax if all of it were taxed at that rate, while the ISA interest remains tax-free.

A quick way to compare two accounts yourself

Start with the amount of annual interest, not just the advertised rate.

1. Calculate gross interest: savings balance × AER.
2. Subtract any available PSA: only the remaining interest is potentially taxable.
3. Apply the relevant savings tax rate to the taxable portion.
4. Compare the net result with the Cash ISA interest, which is tax-free.

For 2026/27 the savings basic, higher and additional rates are 20%, 40% and 45%. The rates applying to savings income are scheduled to rise from 6 April 2027.

What changes from 6 April 2027?

Two announced changes make the comparison more important next tax year.

First, tax rates on savings income are due to rise. From 2027/28, the savings basic rate is set to become 22%, the savings higher rate 42% and the savings additional rate 47%. The Personal Savings Allowance is due to remain £1,000 for basic-rate taxpayers and £500 for higher-rate taxpayers.

Second, the Cash ISA subscription limit is changing. The government has announced a £12,000 annual Cash ISA limit for people under 65 from 6 April 2027, within the overall £20,000 ISA limit. People aged 65 or over are due to retain a £20,000 Cash ISA limit. The detailed regulations are still moving through the final implementation process, so check the updated GOV.UK guidance before relying on the new mechanics.

These changes do not mean every saver should rush money into an ISA before April. They simply increase the value of checking the tax calculation rather than comparing headline AERs alone.

Access matters as much as tax

“Easy access” does not always mean identical access. Some accounts limit the number of withdrawals, reduce the interest rate after withdrawals or use bonus rates that expire. Cash ISAs can have similar product-specific restrictions.

For an emergency fund, compare:

• how quickly you can withdraw;
• whether withdrawals reduce the rate;
• whether there is an introductory or bonus rate;
• minimum and maximum balances;
• whether the Cash ISA is flexible.

A flexible ISA lets you withdraw cash and replace it in the same tax year without the replacement using more of that year’s ISA allowance, subject to the provider’s terms. A non-flexible ISA does not give you that same replacement treatment.

Do not forget FSCS protection

Eligible deposits with a UK-authorised bank, building society or credit union can be protected by the Financial Services Compensation Scheme. The deposit protection limit is currently £120,000 per eligible person, per authorised firm, following the increase that took effect on 1 December 2025.

The important phrase is per authorised firm, not per brand. Two banking brands can share the same banking licence, so balances across them may count towards the same £120,000 limit. Eligible Cash ISA deposits and ordinary savings deposits are covered on the same deposit-protection basis.

When an ordinary easy-access account can make more sense

An ordinary savings account may be the stronger option when:

• it pays materially more than the comparable Cash ISA;
• your expected interest remains within your available tax-free savings allowances;
• you do not need to preserve ISA space for cash;
• its access terms suit your purpose better.

This is especially relevant for smaller balances. If no tax is due, the comparison can be as simple as rate, access and account terms.

When a Cash ISA becomes more valuable

A Cash ISA can become more attractive when:

• your taxable savings interest is already using most or all of your PSA;
• you are a higher- or additional-rate taxpayer;
• you expect your savings balance to grow;
• you want future interest sheltered without having to recalculate the tax position every year;
• you value keeping cash inside the ISA wrapper for later years.

The last point matters because ISA money remains sheltered while it stays inside the wrapper. Building an ISA balance can therefore have a longer-term value that is not captured by comparing only this year’s interest.

What about moving money from a savings account into a Cash ISA?

You can pay new money into a Cash ISA subject to the annual subscription rules. If money is already inside an ISA and you want to move it to another ISA provider, use the receiving provider’s formal ISA transfer process rather than simply withdrawing it and paying it back yourself.

Withdrawing from a non-flexible ISA and then trying to replace the money can use additional ISA allowance. Formal transfer rules are designed to preserve the tax wrapper.

A practical decision checklist

So which is better?

There is no universal winner. If your interest is tax-free anyway, the higher AER can matter more than the ISA label. If tax is taking a meaningful slice of your interest, the Cash ISA can win even when its headline rate is lower.

The cleanest comparison is therefore after-tax interest + access terms + ISA flexibility + deposit protection, not simply “ISA versus non-ISA”.

Official and independent sources checked

• GOV.UK – tax on savings interest and Personal Savings Allowance
• GOV.UK – ISA overview and 2026/27 allowance
• GOV.UK – how ISAs work
• GOV.UK – ISA withdrawals and flexible ISAs
• HMRC – savings tax rates from April 2027
• HMRC – Cash ISA reform from April 2027
• FSCS – current deposit protection limit
• MoneyHelper – choosing savings accounts and Cash ISAs