Corporation Tax self-assessment (CTSA): Assessments: Normal due date unaffected
TMA70/S59D and ICTA88/S10 (1)(a)
The normal due date for CT is nine months and one day after the end of the accounting period. Nothing in the CTSA or CTPF rules alters this date.
For accounting periods ending on or after 1 July 1999, however, “large” companies have to pay their tax in instalments (see CTM92500 onwards).