UK Corporation Tax Calculator 2026
Build an indicative current Corporation Tax computation from accounting profit to taxable total profits, marginal relief, current tax charge and tax payable.
Scope: This tool covers standard UK current Corporation Tax calculations. It does not calculate deferred tax, prepare or submit a CT600, determine transfer pricing, R&D, patent box, CIR, diverted profits, ring-fence, tonnage tax or other specialist regimes.
Calculation result
Current Corporation Tax computation
Accounting profit to trading result
Taxable total profits
Corporation Tax calculation
| Financial year segment | Taxable profits | Adjusted limits | Tax before relief | Treatment | Tax |
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Capital allowances
Current tax reconciliation
Current tax account
Calculation guide
How the UK Corporation Tax calculator works
1. Adjust accounting profit
Start with profit or loss before tax, add back non-deductible costs and deduct allowable tax items. Depreciation is normally added back before capital allowances are claimed.
2. Determine taxable profits
Combine adjusted trading profit with non-trading finance income, property profit, chargeable gains and other taxable income, then apply available reliefs.
3. Apply the correct rate
Use augmented profits, period length and associated companies to test the small-profits rate, marginal relief and main rate.
UK Corporation Tax rates for 2026
For a standard company, the small-profits rate is 19% and the main rate is 25%. Marginal relief can apply where augmented profits fall between the adjusted £50,000 lower limit and £250,000 upper limit. A close investment-holding company is generally charged at the main rate.
Corporation Tax marginal relief calculation
The statutory marginal-relief formula uses the fraction 3/200 and compares augmented profits with the upper limit. Taxable total profits are not always the same as augmented profits because relevant exempt distributions may be added for the threshold test. The limits are divided by the number of associated companies, including the company itself, and time-apportioned for a short accounting period.
Corporation Tax calculator examples
£40,000 profits
With a full 12-month period, no associated companies and no relevant distributions: £40,000 at 19% gives £7,600.
£100,000 profits
At 25%, gross tax is £25,000. Marginal relief is £2,250, giving Corporation Tax of £22,750.
£300,000 profits
Profits exceed the upper limit, so £300,000 at 25% gives £75,000.
One associated company
The full-year limits reduce to £25,000 and £125,000. Tax on £100,000 is £24,625 after marginal relief.
Accounting profit bridge
£100,000 PBT plus £20,000 depreciation and £2,000 entertaining, less £25,000 capital allowances, gives taxable adjusted profit of £97,000.
Corporation Tax adjustments from accounting profit
Accounting profit is the starting point, not the tax result. Typical adjustments include depreciation, non-deductible entertaining, fines, provisions, pension timing differences and capital allowances. Each amount should be entered once. Property income, non-trading loan relationship credits and gains shown separately are removed from the trading bridge and added once in their correct category.
Capital allowances in 2026
The professional mode supports the Annual Investment Allowance, full expensing, the 50% first-year allowance for qualifying special-rate expenditure, the 40% first-year allowance for qualifying main-rate expenditure from 1 January 2026, main and special-rate pools, and the Structures and Buildings Allowance. The main-pool writing-down rate changes from 18% to 14% on 1 April 2026, so a straddling accounting period uses a hybrid rate.
Trading losses and other Corporation Tax reliefs
Loss use depends on the type, period, claim and statutory restrictions. This tool applies only amounts entered and does not make automatic carry-back or group-relief elections. The £5 million deductions allowance and 50% carried-forward loss restriction can require a more detailed computation.
Quarterly instalment payments
Companies above the adjusted large or very-large profit thresholds may need to pay Corporation Tax by quarterly instalments. Associated companies and short periods reduce those thresholds, and exceptions can apply. The result therefore says that instalments may apply rather than asserting a payment schedule.
Current tax vs deferred tax
Current tax is the Corporation Tax payable or recoverable for taxable profits in the period. Deferred tax addresses future tax effects of temporary differences between accounting carrying amounts and tax bases. This calculator produces current-tax schedules only. Use a separate deferred tax computation for FRS 102 or other reporting-framework requirements.
Frequently asked questions
What is the UK Corporation Tax rate for 2026?
The main rate is 25% and the small-profits rate is 19% for a standard company, with marginal relief between adjusted limits. Special regimes can differ.
How does Corporation Tax marginal relief work?
Tax is initially calculated at the main rate, then reduced by the statutory formula. The formula uses augmented profits, the adjusted upper limit and the 3/200 fraction.
Do associated companies reduce Corporation Tax thresholds?
Yes. Divide the limits by the total number of associated companies including the company. A company associated during any part of the accounting period can count for that period.
What is the difference between current tax and deferred tax?
Current tax relates to taxable profits and tax payable for the period. Deferred tax relates to future tax effects of temporary differences. This tool calculates current Corporation Tax only.
Can I use accounting profit as taxable profit?
Not usually. Accounting profit must be adjusted for tax rules, including disallowable costs, exempt items, capital allowances, separate income categories, losses and reliefs.
Does this calculator prepare a CT600?
No. It provides an indicative computation for review. Use suitable tax software and check the return, claims and attachments before submission.
Technical sources
- GOV.UK: Corporation Tax rates and allowances
- HMRC: Corporation Tax Marginal Relief
- HMRC Company Taxation Manual CTM03925
- GOV.UK: capital allowance rates and pools
- HMRC: carried-forward Corporation Tax losses
- HMRC: Corporation Tax instalment payments
Rates and methodology reviewed 3 September 2026.
Professional use: This is a decision-support calculation based on the facts entered. It is not a tax return, legal opinion or substitute for reviewing legislation, HMRC guidance, claims, elections and the company's complete circumstances.
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