Capital allowances rates for 2026The 2026 capital allowances: £1m AIA, full expensing, the 40% first-year allowance from January 2026, and the main pool rate cut to 14% from April 2026.Corporation tax rates and marginal relief for 2026 to 2027Corporation tax for the year from 1 April 2026: 19% small profits rate, 25% main rate, marginal relief between £50,000 and £250,000, and associated companies.HMRC's accounts and Company Tax Return service has closedThe joint HMRC and Companies House service for filing company accounts and the CT600 closed on 31 March 2026. What companies and agents use now.CT600 supplementary pages and when each one is neededThe CT600 supplementary pages from CT600A to CT600P: what each is for, which companies need it, and how the pages fit into the Company Tax Return.Associated companies and the corporation tax limitsHow associated companies are counted from 1 April 2023, the control test, which companies are ignored, and how the £50,000 and £250,000 limits divide.Corporation tax trading losses and how to use themTrading losses: current year and 12-month carry back, carry forward since April 2017, the £5 million deductions allowance, terminal relief and group relief.Research and development relief for accounting periods from April 2024R&D relief from 1 April 2024: the 20% merged scheme credit, enhanced support for intensive SMEs, the claim notification, additional information and CT600L.Close companies and the section 455 charge on loans to participatorsWhat a close company is, the 35.75% section 455 charge on loans made from 6 April 2026, repayment within 9 months, the 30-day rule, section 458 relief and CT600A.Dividends and distributable reservesWhen a company can pay a dividend under the Companies Act 2006, which accounts to rely on, unlawful dividends, the paperwork, and the 2026-27 dividend tax rates.Corporation tax payment dates, instalments and interestWhen corporation tax is due, quarterly instalments for large and very large companies, the payment reference, and HMRC's late payment and repayment interest.Registering a company for corporation taxTelling HMRC a company is active for corporation tax within 3 months, the information HMRC needs, the 10-digit UTR, and dormant companies yet to trade.Corporation tax penalties for late returns and inaccuraciesCompany Tax Return late filing penalties doubled for returns due from 1 April 2026: £200, £400, the 10% tax-based penalties, repeat lateness and inaccuracies.
Corporation tax
Corporation tax for small companies: the rates and marginal relief, capital allowances, the CT600 supplementary pages, associated companies, losses, research and development relief, loans to participators, dividends, registering, paying and penalties.