Occasionally, you may need to process a week 53, or the equivalent period for other non-weekly frequencies, depending on earnings periods and the tax year.
In these circumstances, the following will be true:
Tax will be calculated on a non-cumulative basis, ignoring previous taxable pay and tax paid, which may result in an underpayment of tax. Your employees may later receive a P800 form from HMRC notifying them of this underpayment.
National insurance contributions will be calculated the same as any other period, as NICs are always non-cumulative.
Period director NIC will recalculate cumulatively in both weeks 52 and 53.
Cumulative directors' NIC will be calculated cumulatively in week 53.