UK Corporation Tax & Marginal Relief Calculator (2026/2027)
Calculate your CT600 liability across the 19% Small Profits Rate, 25% Main Rate, and exact Marginal Relief bracket.
Live Step-by-Step Corporation Tax Walkthrough
Line-by-line proof of how HMRC calculates your CT600 liability based on your selected inputs.
💡 Limits are divided by 1 associated company structure.
💡 Profits between £50,000 & £250,000 qualify for Marginal Relief.
💡 Formula: (250,000 - 120,000) × 3/200.
💡 Payment due 9 months and 1 day after company accounting year end.
UK Corporation Tax Rates & Thresholds (2026/2027)
Official HMRC Corporation Tax rates, Marginal Relief fraction, and payment deadlines.
| Profit Bracket | Taxable Profit Range | Headline CT Rate | Marginal Relief Formula |
|---|---|---|---|
| Small Profits Rate | Profits up to £50,000 | 19% | No Marginal Relief needed (Flat 19%) |
| Marginal Relief Band | £50,001 – £250,000 | 19% to 25% Effective | (£250,000 - Taxable Profit) × 3/200 |
| Main Rate | Profits over £250,000 | 25% | Flat 25% on full taxable profits |
Understanding UK Corporation Tax Rules & Filing
Key insights into CT600 preparation, allowable deductions, capital allowances, and deadlines.
How Marginal Relief Works for UK Limited Companies
Under the UK tax regime introduced by HMRC, companies with profits between £50,000 and £250,000 do not pay a flat 25% tax. Instead, they receive Marginal Relief, which gradually increases their effective tax rate from 19% up to 25%.
The formula applies a fraction of 3/200 to the difference between the upper limit (£250,000) and your actual taxable profit.
CT600 Payment & Filing Deadlines
Unlike Individual Self Assessment, Corporation Tax has a dual deadline system:
- Tax Payment Deadline: 9 months and 1 day after your accounting period ends.
- CT600 Filing Deadline: 12 months after your accounting period ends.
Frequently Asked Questions (Corporation Tax)
Need CT600 Preparation & Marginal Relief Tax Filing?
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