CTM92010 - Corporation Tax self-assessment (CTSA): the payment obligation: Due dates
CT is normally due and payable nine months and one day from the end of an accounting period. »Ê¹ÚÌåÓýappre are examples at CTM01800, which reflect the legal position under CTSA and CT Pay & File.
For earlier accounting periods the extra day beyond nine months was allowed by concession.