CTM92580 | CTSA: quarterly instalments: due dates: accounting period less than 12 months
From HM Revenue & Customs · Company Taxation Manual
When the accounting period is less than twelve months:
the final instalment is due, as normal, three months and 14 days after the end of the accounting period,
earlier instalments are due only if the earlier dates mentioned above fall before the due date for the final instalment.
This means that an accounting period of:
three months or less,
needs only the final instalment,
between three months one day and six months,
needs only a first and a final instalment,
between six months one day and nine months,
needs a first, a second and a final instalment,
more than nine months,
needs all four instalments.
The leap year point illustrated in Example 3 in CTM92570 affects the final instalment due date for a short accounting period that ends on 16 November.