File the Corporation Tax return (CT600)
Your company's Corporation Tax return, the CT600, must be filed with HMRC within twelve months of the end of its accounting period, with the accounts and tax computations attached. The tax itself is due earlier, nine months and one day after the period ends.
Who it applies to
Every limited company that HMRC has asked for a return, which is every active company.
What has to happen
The return comes from the same accounts as the Companies House filing and the tax payment, so in practice all three are done together, well inside the twelve months.
If you miss it
For a return due on or after 1 April 2026: £200 the day after the deadline and another £200 at three months, then 10% of the unpaid tax at six months and another 10% at twelve. A third consecutive late return raises the two £200 penalties to £1,000 each.
For a return due before 1 April 2026 the fixed penalties were £100 and £100, or £500 each for a third consecutive late return. Source: gov.uk and Companies House guidance, checked September 2026.
What to do
Enter your year end below for the date. Buzz files the return with the accounts, months before this deadline.
Other dates in this area
- Depends on your datesPay Corporation TaxCorporation TaxDetails
