Corporation Tax Calculator
Calculate your UK company's corporation tax. See how marginal relief affects profits between £50k and £250k.
Updated for 2025/26 tax year
Company Details
Your company's taxable profit for the year
Companies under common control share the rate thresholds
Quick amounts:
Tax Calculation
Marginal Relief Applies
Your profits fall between £50,000 and £250,000, so marginal relief reduces your effective rate from 25% to 21.5%.
Want AI to track this for you?
AccountsOS calculates your corporation tax in real-time as you record transactions. Know exactly what you owe at any moment.
Get Started FreeHow UK Corporation Tax Works in 2025/26
Corporation tax is the tax your limited company pays on its profits. The current rates depend on how much profit your company makes:
- 19% small profits rate — For profits up to £50,000
- 25% main rate — For profits over £250,000
- Marginal relief — For profits between £50,000 and £250,000
What is Marginal Relief?
Marginal relief is a tapering mechanism that gradually increases your effective tax rate from 19% to 25% as profits rise from £50,000 to £250,000. This prevents a sudden jump in tax when crossing the threshold.
Associated Companies
If you control multiple companies, the thresholds are divided between them. For example, with 2 associated companies, the small profits rate applies up to £25,000 each (£50,000 ÷ 2).
Disclaimer: This calculator provides estimates only. Tax rules change and individual circumstances vary. Consult a qualified accountant for advice specific to your situation.
Frequently Asked Questions
How This Calculator Works
This calculator applies the UK Corporation Tax rules for the 2025/26 financial year to determine how much tax your limited company owes on its taxable profits. The calculation follows a three-tier structure:
Small Profits Rate (19%)
Applied when your taxable profits are at or below £50,000. This is the lowest rate and applies to the majority of UK micro-businesses and solo-director companies.
Main Rate (25%)
Applied when taxable profits exceed £250,000. Every pound of profit is taxed at the full 25% rate with no relief.
Marginal Relief (£50,000 to £250,000)
For profits in this range, the calculator first applies the 25% main rate, then subtracts marginal relief using the formula: 3/200 x (£250,000 - profits). This produces an effective rate that gradually increases from 19% to 25%. The marginal rate on each additional pound in this band is 26.5%.
If you have associated companies, the £50,000 and £250,000 thresholds are divided equally between all companies under common control. The calculator adjusts these limits automatically based on the number you enter.
Worked Example: £100,000 Profit
Suppose your limited company has taxable profits of £100,000 for the year ended 31 March 2026 with no associated companies. Here is how the calculation works step by step:
Without marginal relief, you would pay £25,000 at the full 25% rate. Marginal relief saves you £2,250, reducing the effective rate from 25% to 22.75%. If this same company had one associated company, the thresholds would halve, and this £100,000 profit would be taxed at the full 25% main rate.
When to Use This Calculator
Year-End Tax Planning
Estimate your Corporation Tax liability before your accounting period ends so you can plan cash flow and consider strategies like pension contributions or capital purchases to reduce taxable profits.
Setting Aside Tax Reserves
Corporation Tax is due 9 months and 1 day after your accounting period ends. Use this calculator to work out how much to set aside each month so you are not caught short.
Salary vs Dividend Decisions
Salary is a deductible expense that reduces taxable profit. Understand how much CT you save by paying yourself salary vs dividends, especially in the marginal relief band.
Evaluating Associated Company Impact
If you are considering setting up a second company or already control multiple entities, see how the shared thresholds affect your overall tax position.
Important Considerations for 2025/26
Payment Deadline
Corporation Tax is due 9 months and 1 day after the end of your accounting period. For a year ending 31 March 2026, payment is due by 1 January 2027. Late payment incurs automatic interest charges and potential penalties.
CT600 Filing Deadline
Your CT600 Corporation Tax return must be filed within 12 months of the accounting period end. For a year ending 31 March 2026, the filing deadline is 31 March 2027. Note that the payment deadline comes before the filing deadline.
Quarterly Instalment Payments
Companies with profits over £1,500,000 (or £1,500,000 divided by the number of associated companies) must pay Corporation Tax in quarterly instalments during the accounting period rather than 9 months after year-end.
The 26.5% Marginal Rate Trap
While the effective rate in the marginal relief band ranges from 19% to 25%, the marginal rate on each additional pound of profit between £50,000 and £250,000 is actually 26.5%. This means reducing your profits to just below £50,000 can be particularly tax-efficient if you are close to the boundary.
Reducing Taxable Profits
Legitimate strategies to reduce your Corporation Tax bill include paying director salaries, making employer pension contributions, claiming capital allowances on equipment purchases, and carrying forward trading losses from previous years.
Related Resources
Corporation Tax Deadline Guide
Key dates, penalties, and how to never miss a CT payment.
CT600 Corporation Tax Return
Step-by-step guide to completing and filing your CT600.
What Is the Corporation Tax Rate for 2025?
Full breakdown of the 19%, 25%, and marginal relief rates.
When Is Corporation Tax Due?
Payment deadlines, quarterly instalments, and late payment penalties.
Salary vs Dividend Calculator
Find the optimal salary/dividend split to minimise your combined CT and personal tax.
Capital Allowances Guide
Reduce taxable profits by claiming allowances on business assets.