Tax Periods are set by the HMRC. They can be Weekly / Monthly / 2 Weekly / 4 Weekly / Quarterly / Annual / Bi-annual
Tax Period months always run from the 6th of one month to the 5th of the next month.
The 1st tax month runs from 6th April to 5th May.
The 2nd tax month runs from 6th May to 5th June and so on.
Similarly Tax Period weeks are periods of seven days starting from 6th April.
The 1st tax week runs from 6th April to 12th April.
The 2nd tax week runs from 13th April to 19th April and so on.
Your own Pay Periods, the 'From' and 'To' dates on your payslips, may not however coincide with these Tax Period dates i.e. your monthly Pay Period may run from the first to the last day of the month, or perhaps the 24th of one month to the 23rd of the next etc.
When you process your payroll, whichever Tax Period the last day of your Pay Period falls within is the Tax Period which will be updated on your Employer Payment Record - EPR (P32 replacement).
e.g. If your monthly Pay Period runs from 1st May to 31st May. The last day, the 31st May, falls within tax month 2 which runs from 6th May 2020 to 5th June. Therefore, when you run your monthly return for this Pay Period, the Tax Period of month 2 will be updated on the Employer Payment Record - EPR (P32 replacement)