The HMRC have updated the CWG2 Employer guide to reflects some errors corrections.
One area was section 3.1.5
Whilst the opening section was correct (and not changed):
The example 3 retained last years guidance and indicated using a prior tax year rate for starter earning from the prior tax year but paid in the new. The NI rates and threshold are set by the contractual payment date of the actual payment.
Of course, sometime new starters miss the payroll cut-off and so the first actual payment includes the current period pay and a portion of pay from the start period. The guidance indicates the correct action when spanning two tax years:
The example following originally incorrectly referenced using 2019 to 2020 for the March element of pay. This has now been corrected to reflect the tax year as it relates to the point of payment:
This operation results in the correct NI history population in relation to qualification for state benefits such as pension.