GUIDE — DATES AND PERIODS
Three different numbering systems run at the same time, and none of them is wrong. That is why the week number on your payslip so often disagrees with the week number on your rota.
“A tax year is a period starting on 6 April in one year and ending on 5 April in the following year.”
— HMRC, Employer further guide to PAYE and NICs, checked 19 October 2026
So the 2026 to 2027 tax year runs from 6 April 2026 to 5 April 2027. Anything that counts “this year’s” pay, tax or year-to-date figures ends on 5 April.
“Tax weeks are periods of 7 days which follow on from each other starting on 6 April each year. The first tax week is 6 April to 12 April inclusive, the second tax week is 13 April to 19 April inclusive, and so on.”
— HMRC, Employer further guide to PAYE and NICs, checked 19 October 2026
| Tax week 1 | 6 April – 12 April |
|---|---|
| Tax week 2 | 13 April – 19 April |
| Tax week 25 | 21 September – 27 September |
| Tax week 52 | 29 March – 4 April |
Because a tax year is not exactly 52 weeks, the leftover day (or two in a leap year) is treated as a whole week: tax week 53. A weekly-paid employee can therefore have 53 paydays in a tax year, a fortnightly-paid employee 27 (week 54) and a four-weekly-paid employee 14 (week 56).
“Income Tax months are periods following on from each other in an Income Tax year. They start on the sixth of one month and finish on the fifth of the following month.”
— HMRC, Employer further guide to PAYE and NICs, checked 19 October 2026
So tax month 1 is 6 April to 5 May, tax month 2 is 6 May to 5 June, and so on. A “month” on a payslip is often this tax month, not the calendar month — which is why a monthly payslip dated 25 April can belong to tax month 1 while a calendar month has barely started.
This is the point that explains most confusion. HMRC guidance on working out PAYE says to use the tax week that includes the date of payment. The week number on the payslip therefore describes when you were paid, not when you worked.
Two consequences worth knowing:
Your employer chooses the pay day and the period the payslip covers. It can be weekly, fortnightly, four-weekly or monthly, and it can start and end on any weekday. None of that has to line up with the tax week, the tax month, or the days your rota calls “week 1”.
A “duty week” on a rota is a fourth thing again: it is a label your employer uses for a block of duties, and it need not correspond to any tax or calendar week.
| Tax year | 6 April to 5 April |
|---|---|
| Tax week | 7 days from 6 April; week 1 is 6–12 April |
| Tax month | The 6th to the 5th of the next month |
| Pay period | Whatever your employer's payroll uses — any weekday to any weekday |
| Duty week | Your employer's own label for a rota block |
If you compare “this week’s shifts” with “this week’s payslip” using a calendar week, you will often be comparing two different periods — and then the hours look wrong when they are fine.
The reliable approach is to use the period the payslip itself states, and compare the shifts inside that period. If a number still does not match, the likely reasons are in why your payslip hours don’t match your shifts.
Quotes above come from HMRC’s published PAYE guidance, linked and dated. This page is an explanation, not legal or tax advice; your payslip and HMRC remain the record.
A tax year starts on 6 April in one year and ends on 5 April in the following year. The 2026 to 2027 tax year runs from 6 April 2026 to 5 April 2027.
Tax weeks are periods of 7 days following on from each other starting on 6 April. The first tax week is 6 April to 12 April, the second is 13 April to 19 April, and so on.
The one that contains the date of payment. HMRC guidance says to use the tax table for the tax week that includes the date of payment, so the week number follows the pay date rather than the dates you worked.