A company must deliver its return not later than the filing date
(FA98/SCH18/PARA14). (In practice, you may also need to consider
ESC/B46, under which you do not charge a late filing penalty if the
return is in the Revenue's hands soon after the statutory filing
The filing date for a company tax return is the last day of whichever of the following periods is the last to end:
Paragraph 14 (2) defines 'relevant period of account'. It means
in relation to a return for an accounting period, the period of
account of the company in which the last day of that accounting
period falls. There are examples at CTM93050.
See the On-line Company Tax Manual (COM) 'Notices and Returns' business area about the need to notify the computer when the third or fourth bullet applies.