Work out your company's Corporation Tax, with marginal relief, associated companies and short or long accounting periods, plus the dates to pay and file. No sign-up.
Rates. Profits up to £50,000 pay the 19% small profits rate. Profits of £250,000 or more pay the 25% main rate. In between, we work out tax at 25% and take off marginal relief of 3/200 × (£250,000 − profit). We assume your profit doesn't include dividends from companies outside your group, which would count towards the limits.
Limits. Both limits are divided by 1 plus the number of associated companies. For a period shorter than 12 months they're reduced in proportion, the way HMRC does it: the days of the period in each financial year over the days in that year, which is 366 for a year containing 29 February. A full 12-month period keeps the full limits.
Long periods. Accounts longer than 12 months are two accounting periods: the first 12 months and the rest. We split the profit by days unless you enter the first 12 months' figure, then work out each period on its own.
Dates. Tax is due 9 months and 1 day after each accounting period ends. The CT600 is due 12 months after the period ends, or, for accounts of up to 18 months, 12 months after the accounts end. We don't model quarterly instalments for large companies.
Not covered. Periods starting before 1 April 2023, when a single rate applied, and accounts longer than 18 months. Close investment-holding companies pay the main rate whatever their size, and ring-fence (oil and gas) profits have their own rates.
Official sources: Corporation Tax rates · Marginal Relief guidance · HMRC's Marginal Relief calculator · HMRC on apportioning the limits · Accounting periods · Pay Corporation Tax · Company Tax Returns · Paying in instalments
From the Starter plan (£29 a month ex VAT), Ledgers prepares a draft Corporation Tax computation from your books and tracks your director's loan account as you go. It doesn't file the CT600: you or your accountant check the numbers and submit the return to HMRC. See pricing.
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19% (the small profits rate) on profits up to £50,000 and 25% (the main rate) on profits of £250,000 or more. In between, you pay the main rate less marginal relief, so your overall rate lands between 19% and 25%. These rates have applied since 1 April 2023 and are set until 31 March 2028.
For profits between £50,000 and £250,000, work out tax at 25%, then take off 3/200 of the gap between £250,000 and your profit. On £100,000 that's £25,000 less £2,250, so £22,750. Each extra pound of profit in this band costs 26.5p in tax.
Another company that controls yours, that yours controls, or that is under the same person's control, at any time in the accounting period. The £50,000 and £250,000 limits are divided by 1 plus the number of associated companies, so with one they become £25,000 and £125,000. A company that didn't carry on any trade or business in the period doesn't count.
Pay 9 months and 1 day after the end of your accounting period: for a year to 31 March, that's 1 January. The Company Tax Return (CT600) is due 12 months after the period ends. Companies with profits over £1.5 million a year usually pay in quarterly instalments instead.
An accounting period for Corporation Tax can't be longer than 12 months, so accounts of up to 18 months become two: the first 12 months and the rest. Profit is usually split between them by days. Each period has its own tax bill, due 9 months and 1 day after it ends, and its own return. Both returns are due 12 months after the accounts end.
The £50,000 and £250,000 limits are reduced in proportion to the length of the period. HMRC counts the days of the period in each financial year (1 April to 31 March) against the days in that year, using 366 when the year contains 29 February.
Related: What is Corporation Tax and when do I pay it? · Salary vs dividends calculator · Director's loan (s455) calculator · How to pay dividends · Director's loan accounts
An estimate, not tax advice. Based on GOV.UK and HMRC guidance as at 13 October 2026. Your actual liability depends on your full tax computation; check it with your accountant or HMRC before you pay or file.