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HMRC internal manual

Company Taxation Manual

CTSA: quarterly instalments: very large companies: amounts due at each instalment: formula

The amount of a very large company’s liability that is due on the instalment dates (“CTI”) is the total liability as calculated under paragraph 8(1) of Schedule 18 Finance  Act 1998 (which includes tax charged in respect of controlled foreign companies and the Bank CT surcharge) but excluding the following:

  • bank levy
  • CT or supplementary charge on ring fence profits and adjusted ring fence profits of oil and gas companies.

If there is only one payment date, the whole of the liability is due on that date.

If there is more than one instalment date:

  • the amount due on the first instalment date is the lesser of CTI and the amount given by the formula below.
  • the amounts due on the second and third instalment dates is the lesser of CTI - B and the amounts given by the formula below.  B is the amount of the liability due to be paid on the previous instalment dates.
  • the amount payable on the final instalment date is CTI - B.

The formula is:

3 x (CTI /(wm + wmd))


  • “wm” is the number of whole months falling within the accounting period;
  • “wmd” is the decimal (calculated to two places rounded arithmetically where necessary) of the fraction R/30, where “R” is the number of days in an accounting period outside the whole months represented by “wm”.