UK Corporation Tax is charged on the taxable profits of limited companies. Since April 2023 there are two headline rates — 19% for smaller profits and 25% for larger ones — with marginal relief smoothing the step between them.
Rates, thresholds and deadlines below are correct at the time of writing. HMRC updates them regularly, so confirm the current figures on GOV.UK or with your accountant before you file or pay. This guide is general information, not tax advice.
| Profits | Rate |
|---|---|
| Up to £50,000 | 19% (small profits rate) |
| £50,001 to £250,000 | 25% less marginal relief (effective rate between 19% and 25%) |
| Over £250,000 | 25% (main rate) |
Between £50,000 and £250,000 you pay the main rate of 25%, then deduct marginal relief so the effective rate rises gradually from 19% to 25%. The relief is:
Marginal relief = 3/200 × (£250,000 − augmented profits) × (taxable profits ÷ augmented profits)
Augmented profits are taxable profits plus most dividends received from non-group companies. For a company with no such dividends, the two profit figures are the same and the last fraction is 1. Profits in the marginal band are effectively taxed at 26.5% on each extra pound.
ETaxFlow applies the 19%/25% rates and marginal relief automatically and keeps a live tax provision.
The £50,000 and £250,000 limits are divided by 1 plus the number of associated companies. A company with one associated company has limits of £25,000 and £125,000. The limits are also reduced proportionately for accounting periods shorter than 12 months.
| What | Deadline |
|---|---|
| Pay Corporation Tax | 9 months and 1 day after the end of the accounting period |
| File the CT600 return | 12 months after the end of the accounting period |
| File statutory accounts at Companies House | 9 months after the financial year end (private companies) |
| Large companies (profits over £1.5m) | Pay in quarterly instalments instead |
The payment date is three months earlier than the filing date. Missing it means interest, so estimate your liability during the year rather than at filing time.
Client entertainment, most fines and penalties, and depreciation itself (replaced by capital allowances) are added back when computing taxable profit. Flagging these while you post transactions saves rework at year end.
Filing the CT600 even one day late brings an automatic £100 penalty, with further penalties if it is still outstanding after three, six and twelve months. Repeated lateness raises the amounts.
| Step | What happens |
|---|---|
| 1. Track profit monthly | Watch your position against the £50,000 and £250,000 limits |
| 2. Flag non-deductible items | Entertainment and fines identified when posted |
| 3. Keep the fixed asset register current | Feeds capital allowances workings |
| 4. Check associated companies | Adjust the limits if the group structure changed |
| 5. Provide for the tax | Live provision so payment is never a surprise |
| 6. Hand over the workpaper | Accountant finalises and files the CT600 |
19% on profits up to £50,000 (small profits rate) and 25% on profits above £250,000 (main rate), with marginal relief between the two limits.
3/200 × (£250,000 − augmented profits) × (taxable profits ÷ augmented profits). It is deducted from tax at 25% so the effective rate rises gradually from 19% to 25%.
Payment is due 9 months and 1 day after the accounting period ends; the CT600 return is due 12 months after it ends. Large companies pay in instalments.
Yes. The £50,000 and £250,000 limits are divided by one plus the number of associated companies, and reduced for short accounting periods.
ETaxFlow computes the Corporation Tax figures from your accounting records and exports an accountant-ready workpaper. Your accountant completes and files the CT600 with HMRC.