The main rate, small profits rate and marginal relief all affect what your clients pay. Here is a refresher.
Corporation Tax is no longer a single flat rate, so getting the computation right means applying the right rate and any relief.
Rates and thresholds
The main rate applies to companies with profits above the upper limit, while a lower small profits rate applies below the lower limit. Between the two, marginal relief tapers the effective rate. Associated companies reduce those limits, which is easy to miss in groups.
What to watch
Full expensing and the annual investment allowance affect capital allowances claims, and R&D relief rules have tightened. Always confirm current rates, limits and reliefs on GOV.UK when preparing a CT600, as thresholds can change at fiscal events.