Corporation Tax Calculator.
19%, 25%, and the marginal relief band in between — what your company actually pays.
Uses 2026/27 rates: 19% small profits rate to £50,000, 25% main rate from £250,000, marginal relief between — thresholds divided when companies are associated. Everything runs in your browser — your figures never leave it. Estimates are general information, not advice: ask us about your own position.
The company's bill
19%, 25%, and the strange land in between.
Corporation Tax stopped being one number in 2023. For 2026/27 your company pays 19% on profits up to £50,000, 25% from £250,000, and between the two sits marginal relief — a tapering calculation that produces an effective rate somewhere in the middle and a marginal rate of 26.5% on every pound in the band. This calculator does the arithmetic properly: tax at the main rate, minus relief at 3/200ths of the shortfall, with the effective rate on its own line so you can see where you stand.
The detail that catches people: those thresholds are divided among associated companies. Two companies under common control means each hits the 25% band at £125,000, not £250,000. If you run a group — or your spouse runs a company alongside yours — the split matters, and it is exactly the kind of thing we untangle in restructuring work.
Profit is also a choice of timing: pensions, capital allowances, and when expenditure lands can all move a company out of the 26.5% marginal band. That is planning, not filing — and it is where an accountant earns the fee.
Common questions.
What is marginal relief?
A deduction that smooths the jump between the 19% small profits rate and the 25% main rate. Between £50,000 and £250,000 of profit, tax is calculated at 25% and then reduced by 3/200ths of the gap between £250,000 and your profit. The effective rate rises gradually — but each extra pound in the band is taxed at 26.5%, higher than the main rate itself.
What counts as an associated company?
Broadly, companies under common control — the same person or group controlling both, including through certain family and business links. Dormant companies are ignored. Associated companies split the £50,000 and £250,000 thresholds between them, so two associated companies each reach the main rate at £125,000.
When is Corporation Tax due?
For most companies, nine months and one day after the accounting period ends — before the filing deadline for the return itself, which is twelve months. Companies with profits over £1.5m (divided by associated companies) pay by quarterly instalments instead. Our tax calendar tracks your exact dates.
Can I reduce the profit this is calculated on?
Taxable profit is accounting profit with adjustments — and legitimate planning moves it: employer pension contributions, capital allowances including full expensing on qualifying plant, R&D relief where it genuinely applies, and timing of expenditure around year end. That is advisory work, and it is the difference between recording the year and shaping it.
Keep going.
My Tax Calendar
Your company's actual CT, accounts and confirmation dates — found, verified, subscribed.
Open →Dividend vs Salary
Corporation Tax is step one of extraction — see the whole journey to your pocket.
Open →Tax advisory
Planning that moves companies out of the 26.5% band — legitimately, and in advance.
Open →Prefer a human with the numbers?
If your profit is anywhere near £50,000 or £250,000 — or there is more than one company in the picture — the thresholds deserve a proper look.