A large company with taxable profits between £1.5m and £20m is required to pay Corporation Tax in 4 equal instalments. These instalments are payable in months 7, 10, 13 and 16 following the start of the relevant accounting period. The actual payments are due 6 months and 13 days after the start of the accounting period, then 9 months and 13 days, then 12 months and 13 days and finally 15 months and 13 days after the start of the accounting period.