Corporation Tax Calculator
Work out your Corporation Tax including Marginal Relief, and see the effective rate you are actually paying on the profits in between.
- Small profits rate applies up to
- £50,000
- Main rate applies from
- £250,000
- Tax at the 25% main rate
- £30,000.00
- Less Marginal Relief
- −£3,000.00
- Corporation Tax due
- £27,000.00
- Effective rate
- 22.50%
- Profit after tax
- £93,000.00
Assumes a full 12-month accounting period and no distributions from unrelated companies.
The bit in the middle costs 26.5%
Most directors know the headline rates: 19% below £50,000 and 25% above £250,000. Fewer realise what happens in between.
Marginal Relief does not give you a blended rate. Every extra pound of profit between the two limits is taxed at an effective 26.5% — higher than the main rate itself. That is the price of climbing out of the small profits band.
Profit between £50,000 and £250,000 carries a marginal rate of 26.5%, not 25%.
It matters for timing. If your profit is near £250,000, accelerating an expense or deferring income across the year end saves tax at 26.5%, not 25%. If you are near £50,000, the same move saves at 26.5% rather than 19%.
Associated companies are the trap
The thresholds are divided by the number of associated companies plus one. Two companies under common control means the small profits limit falls to £25,000 each and the upper limit to £125,000 each.
This catches people out constantly. A property SPV, a dormant company you forgot about, a separate trading entity set up years ago — each one can drag your other companies into a higher effective rate. Control is judged broadly, and it includes companies controlled by associates such as close family.
Try it above: set the profit to £60,000 and add one associated company. The tax rises even though the profit has not moved.
If you hold property through an SPV alongside a trading company, or you have dormant companies still on the register, the associated company rules may already be costing you. Striking off a genuinely dormant company can be worth real money — but only if it is genuinely dormant and no longer needed.
When it is due
For companies with taxable profits up to £1.5 million, Corporation Tax is due nine months and one day after the end of the accounting period. Larger companies pay by quarterly instalments. The payment deadline and the filing deadline are not the same date, which is a distinction that catches out more directors than it should.
We have written at greater length about why a profitable company can still struggle to pay its Corporation Tax bill.
Real Corporation Tax computations involve capital allowances, disallowable expenditure, losses brought forward, R&D claims and more. This calculator works from a taxable profit figure you supply, which is itself the output of the work.
Speak to us if you want the actual number, or see our annual accounts service.
Rates correct for financial year 2026, which runs from 1 April 2026 to 31 March 2027. Next review April 2027.
This calculator gives a general estimate and is not a substitute for advice on your own circumstances. It assumes a 12-month accounting period, no ring-fence profits, and that your company is entitled to Marginal Relief.