NIM09100 - Earnings Periods: Holiday pay: Method of calculation
Paragraph 2 of Part X to Schedule 3 of the Social Security (Contributions) Regulations 2001 (SSCR 2001) (SI 2001 No 1004)
Include holiday pay in the gross pay figure when calculating NICs, except when it is money previously deducted from the employee’s pay and on which NICs have already been paid or it is paid from an independently managed fund to which more than one employer contributes (see NIM02200).