Corporation Tax Calculator
Work out corporation tax including Marginal Relief and the associated-companies adjustment, for 2026/27, with every step of the relief arithmetic shown.
The figure after disallowed expenses, capital allowances and losses have already been applied — this tool does not compute those adjustments.
Other companies under common control with this one (including dormant companies), not counting this company itself. This divides both limits: 3 associated companies divides £50,000/£250,000 by 4.
A close investment-holding company does not qualify for the Small Profits Rate or Marginal Relief, and pays the main rate on all profits. Note: this is NOT the same as a Community Interest Company — a Community Interest Company is taxed like any other company and does qualify for the small profits rate and marginal relief. Leave this unticked unless your company exists mainly to hold investments.
Ring fence profits use a different rate structure (Ring Fence Corporation Tax and the Supplementary Charge), which this calculator does not cover.
SECONDARYgov.uk — Corporation Tax Marginal Relief guidanceLast checked 2026-04-01