Freedom Isn’t Free UK Personal Finance
Self-Employed
Corporation Tax UK: A Small Company Guide for 2026/27
UK Corporation Tax is 19% on profits up to GBP 50,000 and 25% on profits over GBP 250,000. In between, Marginal Relief tapers the bill, so each pound of profit in the GBP 50,000 to GBP 250,000 band is taxed at an effective 26.5%, higher than the 25% headline.
Corporation Tax rates and effective rates (2026/27)
| Profit band | Headline rate | Effective marginal rate |
|---|---|---|
| Up to GBP 50,000 (small profits rate) | 19% | 19% |
| GBP 50,000 to GBP 250,000 (Marginal Relief) | 25% less Marginal Relief | About 26.5% on each pound in the band |
| Over GBP 250,000 (main rate) | 25% | 25% |
| Marginal Relief fraction | 3/200 | Applied to (upper limit less profits) |
| Register with HMRC | Within 3 months of starting to trade | Failure-to-notify penalty if late |
| Pay Corporation Tax | 9 months and 1 day after the accounting period ends | Interest charged on late payment |
| File the CT600 return | 12 months after the accounting period ends | Penalties from GBP 100 for late filing |
| Associated companies | The GBP 50,000 and GBP 250,000 limits are divided by the number of associated companies | More companies pull you into the higher rate sooner |