Corporation Tax Calculator 2025/26
Calculate your company's corporation tax liability for the 2025/26 tax year.
Calculate Corporation Tax (2025/26)
Corporation Tax Rates 2025/26
For the financial year starting April 2025: Small profits rate (profits up to £50,000): 19%. Main rate (profits over £250,000): 25%. Marginal relief applies for profits between £50,000 and £250,000, with an effective marginal rate of 26.5%. These thresholds are divided by the number of associated companies.
Marginal relief formula: (Upper limit – Profits) × (Upper limit / Lower limit – 1) × Standard fraction. For FY2025: Standard fraction = 3/200. This effectively taxes profits in the £50,000–£250,000 band at 26.5%. R&D tax credits, capital allowances and loss relief can reduce your CT liability.
Frequently Asked Questions
What is the corporation tax rate in 2025/26?
Small profits rate (up to £50,000): 19%. Main rate (over £250,000): 25%. Marginal relief applies for profits between £50,000 and £250,000, with an effective marginal rate of 26.5%.
When is corporation tax due?
For small companies (under £1.5m profits), CT is due 9 months and 1 day after the company's accounting period ends. Large companies pay in quarterly instalments.
What is the marginal relief fraction for 2025/26?
3/200 — this is the standard fraction used to calculate marginal relief for profits between the lower limit (£50,000) and upper limit (£250,000).
How are the CT thresholds divided by associated companies?
The £50,000 lower limit and £250,000 upper limit are divided by (1 + number of associated companies). Two associated companies each have a lower limit of £25,000.
What are associated companies for CT purposes?
Companies under common control — where one controls the other, or both are controlled by the same person or persons. Dormant associates are excluded.
Can I reduce my corporation tax bill?
Yes — through capital allowances (100% Annual Investment Allowance up to £1m), R&D tax credits (86% enhanced deduction for SMEs), loss relief, pension contributions and charitable donations.
What is the Annual Investment Allowance (AIA)?
The AIA gives 100% first-year deduction for qualifying plant and machinery up to £1,000,000 per year. This is permanent as of April 2023 under Budget 2023 measures.
What is the R&D tax credit rate for 2025/26?
SMEs can claim an enhanced deduction of 86% on qualifying R&D costs (was 130% until April 2023). Loss-making SMEs can claim a cash credit of 10%. The RDEC rate for large companies is 20%.
What is the CT600 form?
The CT600 is the corporation tax return submitted to HMRC. It must be filed within 12 months of the accounting period end. Filing deadlines and payment dates are different.
Does corporation tax apply to non-resident companies?
Non-resident companies with UK property income or a UK permanent establishment are subject to UK corporation tax on those UK profits.
What is ring-fence corporation tax?
North Sea oil and gas profits are subject to ring-fence corporation tax at 30% (plus the energy profits levy). Standard CT rates do not apply to ring-fence profits.
When was the 25% main rate introduced?
The 25% main rate was introduced from April 2023, replacing the flat 19% rate. The small profits rate at 19% was maintained for profits up to £50,000.