ISA vs savings account calculator
Compare what a Cash ISA and a taxable savings account would actually pay you, after tax. A higher headline rate outside an ISA does not always win once your Personal Savings Allowance runs out.
From other non-ISA accounts. Uses up your allowance first.
Only needed to work out the 0% starting rate for savings. Leave blank to ignore it.
After tax, each year
Cash ISA interest
£400
Always tax-free.
Savings account interest after tax
£450
Tax: £0
Pays more after tax
The savings account
Break-even savings rate
4.00%
What the savings account would need to pay to match the ISA.
How this works
- ISA interest is always tax-free, so it is simply your amount multiplied by the ISA rate.
- Savings account interest is taxed above your Personal Savings Allowance (£1,000 basic rate, £500 higher rate, £0 additional rate), at your band's savings rate for the tax year you choose.
- If you enter other income, we also apply the separate 0% starting rate for savings, up to £5,000, which shrinks pound for pound once that income passes the £12,570 Personal Allowance and disappears entirely at £17,570. Leave it blank to ignore this: most higher and additional rate taxpayers do not qualify for it anyway.
- Other savings interest you enter is assumed to use up your allowance first, so it reduces how much of the amount you are testing counts as tax-free.
- The break-even savings rate is the rate a taxable account would need to pay to exactly match your ISA's after-tax interest, given everything else you have entered.
- Switching the tax year toggle applies the higher 2027/28 savings rates instead of the 2026/27 rates. The Personal Savings Allowance itself does not change between the two.
- Figures are rounded to the nearest pound, and the break-even rate to the nearest 0.01 percentage point.
For the full picture on how ISAs work, see what is an ISA and our ISA versus savings account guide.
Tax treatment depends on your circumstances and may change. This is not financial advice.
Questions people ask
Why would a savings account with a higher rate ever lose to an ISA?
Because tax only applies outside an ISA. Once your Personal Savings Allowance is used up, a taxable savings account has to earn more than the ISA rate just to match it after tax, so it can lose even with a higher headline rate.
What is the Personal Savings Allowance?
The amount of interest you can earn outside an ISA each year before paying tax on it: £1,000 for basic rate taxpayers, £500 for higher rate, and £0 for additional rate. Interest inside an ISA does not use up this allowance.
What is the starting rate for savings?
A separate 0% band of up to £5,000 for savings interest, on top of your Personal Savings Allowance, available if your other, non-savings income is low. It shrinks pound for pound as that other income rises above the £12,570 Personal Allowance, and disappears once it reaches £17,570.
Should I use the 2026/27 or 2027/28 rates?
Use 2026/27 for the tax year running to 5 April 2027. From 6 April 2027, savings tax rates rise by 2 percentage points, to 22, 42 and 47 percent, so switch the toggle to see the comparison after that date. The Personal Savings Allowance itself is not changing.
Does this calculator account for Scottish income tax?
Yes, indirectly: savings interest is taxed at the same UK-wide rates for everyone, including Scottish taxpayers, because the Scottish Parliament’s income tax powers do not extend to savings or dividend income.