Corporation Tax Calculator

Last reviewed: 22 May 2026

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Calculate UK Corporation Tax using HMRC's post-April 2023 rules with small profits rate (19%), main rate (25%), and marginal relief.

Estimates only – not tax advice. For planning purposes only; does not replace professional advice or official HMRC calculations. Full disclaimer

Inputs

Financial Year

Taxable Profits

Accounting Period (months)

1-12 months. Limits are scaled proportionally.

Number of Associated Companies

Enter the count of other associated companies (not including this one). Limits are divided by total company count.

Full Mode

Full mode applies the current 19% small profits rate, 25% main rate and HMRC's marginal relief fraction (3/200), adjusting the small and large profits limits for associated companies and shorter or longer accounting periods.

Corporation Tax
Marginal relief zone (19-25%)

Corporation Tax Due

£22,750

Effective Rate

22.75%

Marginal Relief Breakdown

CT at main rate (25%)£25,000.00Marginal relief-£2,250.00CT payable£22,750.00

Adjusted Limits

Company count1Lower limit (period)£50,000.00Upper limit (period)£250,000.00

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Assumptions used in this calculation (click to expand)

What this calculator assumes

Single UK-resident close company; no associated companies unless entered.
12-month accounting period — short periods are not pro-rated automatically.
Profits are after R&D, capital allowances, and other deductions (taxable profit, not turnover).
Augmented profits = taxable profits (no franked investment income modelled).

Not included in this calculation

Associated companies dilution of the £50,000 / £250,000 limits.
Short accounting periods or change of accounting date.
Group relief, loss carry-back, or consortium relief.
Patent Box, R&D super-deduction interactions (R&D has its own calculator).
Diverted Profits Tax and corporate interest restriction.

Statutory basis

CTA 2010 s.18A (small profits rate)
CTA 2010 ss.18B–18N (marginal relief)
CTA 2009 (charge and computation)

How this is calculated (click to show the formula)

Marginal relief formula

CT = (Profit × Main rate) − (Upper limit − Profit) × (Profit / Augmented) × Marginal relief fraction

Where Marginal relief fraction = 3/200 for the standard 25%/19% pairing. Profits ≤ £50,000 pay the small profits rate (19%); profits ≥ £250,000 pay the main rate (25%); profits between get marginal relief.

This calculator applies standard Corporation Tax rules only and ignores special reliefs (e.g. R&D, Patent Box). For complex cases, cross-check with your own computations and HMRC guidance.