Corporation tax calculator — small profits, main rate, and the marginal zone.
Enter your company's taxable profit and see corporation tax, effective rate, and which HMRC band you fall into. Covers the 19% small profits rate, the 25% main rate, and the marginal relief taper between £50,000 and £250,000.
Profits between £50,000 and £250,000 are in the marginal relief zone. The effective rate slides from 19% up to 26.5% — the marginal rate across this band is actually higher than the main 25% rate.
Scope: UK corporation tax only (FY 2025/26 rates). Doesn't model associated companies (which lower the thresholds), R&D credits, loss relief, or capital allowances — any of which can move the number materially. Use this as a starting figure, not a final tax return.
Three rates, one tapered middle.
UK corporation tax is structured in three bands. Profits up to £50,000 are taxed at the small profits rate of 19%. Profits of £250,000 and above attract the main rate of 25%. Between those figures — the marginal relief band — the effective rate slides up from 19% towards 25%, but the marginal rate on each additional pound inside the band is actually 26.5%. That's counterintuitive but important: going from £60,000 to £61,000 of profit costs you 26.5p in the pound, not 25p.
The practical implication for Harrow owner-directors is that the jump from small profits to marginal relief is a genuine planning moment — pensions, timing of capital purchases, and owner-director extraction policy all shift around the £50,000 mark. An accountant running the numbers on your specific year-end position will usually save more than they charge to do it.
This calculator doesn't handle associated companies (which reduce both thresholds proportionally), the short accounting period rules, R&D tax credits, capital allowances above the annual investment allowance, or losses brought forward. If any of those apply to you, treat the figure here as an upper-bound estimate only.
A calculator gives a number. An accountant gives a plan.
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