NIM08620 - Earnings Periods: Regular additional payment made later
Regulation 7 of the Social Security (Contributions) Regulations 2001 (SSCR 2001) (SI 2001 No 1004)
If an employer makes a regular additional payment outside the earnings period in which it would normally fall, treat it as belonging to its normal earnings period, except when this is in a different tax year (See NIM08720). The employer must revise any NICs already paid on the other earnings, see NIM08700 onwards.