ISA vs Savings Account Calculator

Correct as of 26 September 2026. The ISA and tax rules on this page were last checked against gov.uk on this date. Figures are for the 2026/27 tax year unless a different year is stated. For every rule with its source, see ISA rules at a glance.

You do not usually pay tax on interest from a cash ISA. Interest from an ordinary savings account is taxable, but most people can earn some interest tax-free under the Personal Savings Allowance. This calculator works out, for one tax year, the tax on the interest from a savings account and compares what is left with the interest from a cash ISA at the rate you enter.

Amount saved (£)Savings account interest rate (%)Cash ISA interest rate (%)Your Income Tax band

More options

Interest from other savings this tax year (£)

Savings account interest after tax

Cash ISA interest (tax-free)

Tax on the savings account interest

One tax year's interest on a balance held all year. Figures are rounded to the nearest pound. Illustrative only, not tax or financial advice.

The calculator assumes the balance and rates stay the same for the whole tax year. Your real tax depends on all your income. Check your position with HMRC or a tax adviser.

Advanced ISA Planner

Compare ISA scenarios side by side

£14.99 one-off, no subscription

Once you have compared an ISA with a savings account, the Advanced ISA Planner can compare two cash and investment splits of the same contributions across several tax years.

When a single calculator is not enough, the Advanced ISA Planner lets you set up longer-term scenarios, combine different ISA types, including cash ISAs, and model multiple tax years in one place.

Combine Cash and Stocks & Shares ISAs
Model multiple tax years and allowances
Adjust returns, contributions, and time horizons
Compare scenarios side by side

Explore the Advanced ISA Planner

A paid tool: a one-off purchase of £14.99, with no subscription. The free calculators are separate from the planner. See the refund policy. Figures are illustrations, not forecasts.

The planner's worked example with its default inputs: three result tiles for two scenarios and the difference between them, above a year-by-year chart of both scenarios with a shaded range — Worked example with the planner's default inputs. Illustrative scenarios, not a recommendation or a forecast.

How much savings interest is tax-free outside an ISA in 2026/27?

Personal Savings Allowance and tax rate on savings interest by Income Tax band, 2026/27
Income Tax band	Interest you can earn tax-free	Tax rate on interest above that
Basic rate	£1,000	20%
Higher rate	£500	40%
Additional rate	£0	45%

If your other income is low, you may also get the starting rate for savings: up to £5,000 of interest tax-free, reduced by £1 for every £1 of other income above your Personal Allowance (£12,570). You cannot get it if your other income is £17,570 or more. The calculator does not include the starting rate, so it may overstate tax for people on low incomes.

Savings interest is taxed at the same rates in Scotland as in the rest of the UK.

How do I read the result?

Savings account interest after tax: the interest for the year, minus tax on the part above your remaining Personal Savings Allowance.
Cash ISA interest: the interest at the ISA rate you entered, with no tax to pay.
Equivalent rate: the savings account rate that would leave you with the same interest after tax as the cash ISA. If a savings account pays more than this, it would come out ahead in the scenario you entered.
Other interest: interest from other accounts uses up the same allowance. Add it under "More options".

Which ISA limits apply?

You can pay up to £20,000 into ISAs in 2026/27. Regulations made on 10 September 2026 (SI 2026/1018, read on legislation.gov.uk on 6 October 2026) provide that from 6 April 2027, savers who are under 65 at the end of the tax year will be able to pay up to £12,000 a year into cash ISAs, within the overall ISA allowance. From the start of the tax year in which they turn 65, savers will be able to pay up to £20,000 a year into cash ISAs.Cash savings above a cash ISA limit would need to be held outside an ISA, where this calculator can show the tax on the interest. The guide to the cash ISA changes explains the details.

Frequently asked questions

Do I pay tax on interest from a cash ISA?

You do not usually pay tax on interest from a cash ISA. Interest from an ordinary savings account is taxable, but many taxpayers have a Personal Savings Allowance, and its size depends on the tax band.

How much savings interest is tax-free in 2026/27?

Under the Personal Savings Allowance, the interest you can earn tax-free is £1,000 for a basic-rate taxpayer, £500 for a higher-rate taxpayer and £0 for an additional-rate taxpayer. Interest above that is taxed at 20%, 40% or 45% respectively.

What is the starting rate for savings?

If your other income is low, you may also get the starting rate for savings: up to £5,000 of interest tax-free, reduced by £1 for every £1 of other income above your Personal Allowance (£12,570). You cannot get it if your other income is £17,570 or more. The calculator does not include the starting rate, so it may overstate tax for people on low incomes.

What does the equivalent rate mean?

It is the savings account rate that would leave you with the same interest after tax as the cash ISA at the rate you entered. If a savings account pays more than this, it would come out ahead in the scenario you entered. Interest from other accounts uses up the same allowance, so add it under "More options".

How much can be paid into a cash ISA?

You can pay up to £20,000 into ISAs in 2026/27. Regulations made on 10 September 2026 (SI 2026/1018, read on legislation.gov.uk on 6 October 2026) provide that from 6 April 2027, savers who are under 65 at the end of the tax year will be able to pay up to £12,000 a year into cash ISAs, within the overall ISA allowance. From the start of the tax year in which they turn 65, savers will be able to pay up to £20,000 a year into cash ISAs. Cash savings above a cash ISA limit would need to be held outside an ISA, where this calculator can show the tax on the interest.

Is this tax or financial advice?

No. The calculator assumes the balance and rates stay the same for the whole tax year, and your real tax depends on all your income. It gives general information only, not tax or financial advice or a recommendation of any product. Check your position with HMRC or a tax adviser.

Sources

This calculator gives general information only. It is not tax or financial advice or a recommendation of any product.