National Insurance on Back Pay

RacingDriver

I started a new job in January but missed the payroll cut-off for the month.

So in February, I have been paid both my January and February pay.

Should NI have been calculated as two separate months, or as one month?

If it makes any difference the two months are listed separately on my Feb payslip (Salary & Salary Adj)

chrisbur

Yes should be calculated separately; covered in this guidance for employers....

https://www.gov.uk/government/publications/cwg2-further-guide-to-paye-and-national-insurance-contributions/2017-to-2018-employer-further-guide-to-paye-and-nics

Section 3.1.5 example 2

"Example 2
A new employee starts work on 9 June and is due to be paid monthly on the last day of each month. The earnings period is monthly and the first payday is 31 July (mistimed payments). The employee receives £2,250 gross pay which is made up of:

£750 for the period 9 June to 30 June
£1,500 for the period 1 July to 31 July
Work out National Insurance contributions separately on the payment for:

June of £750 and record National Insurance contributions on the employee’s payroll record in tax month 3
July of £1,500 and record National Insurance contributions on the employee’s payroll record in tax month 4"