There is no single legal method for paying a part month, which is why two people starting the same job on the same day at two employers can be paid different amounts. The three methods in common use are calendar days, working days in that month, and 1/260ths of the annual salary. On a £30,000 salary and a start on Monday 14 September 2026, they pay £1,397.26, £1,477.27 and £1,500.00 for the same 13 worked days: a spread of £102.74, entirely down to which divisor your employer's payroll uses.
Calendar days: annual salary divided by 365
The most common method in the UK takes the annual salary, divides by 365 and multiplies by the calendar days you were employed, weekends and all. Starting on 14 September 2026 means 17 calendar days of employment in a 30-day month, so £30,000 divided by 365 is £82.19 a day, and 17 days is £1,397.26. Because it counts every day of the year rather than every working day, a month with a bank holiday or a long weekend at the start is worth slightly less on this method than on the others, and February pays a little less per calendar day than it should feel like.
Working days in that month: a twelfth, scaled
The second method takes a normal month's pay and scales it by the working days you covered. September 2026 has 22 weekdays; starting on Monday 14 September leaves 13 of them. A twelfth of £30,000 is £2,500.00, and 13 of 22 working days is £1,477.27. This method is the fairest one on a short month and the harshest on a long one, because the divisor moves with the calendar: the same 13 days in a 20-working-day month would pay £1,625.00, and in a 23-working-day month £1,413.04. If your employer uses it, your first payslip depends on which month you happened to start.
The 1/260th method: one day is always worth the same
The third method fixes a working year at 260 days, five days a week for 52 weeks, and pays one 260th of the annual salary for each working day. £30,000 divided by 260 is £115.38 a day, so 13 days is £1,500.00. It is the only one of the three where a day is worth the same in every month, which makes it the easiest to check and the easiest to argue with, and it is the method the calculator on this site assumes when it converts a salary to a daily figure. It pays slightly more than the other two on most months because 260 is a shade fewer days than the average month-scaled count.
What happens to the tax on a part month
PAYE is cumulative, so a part month is not taxed as though it were your whole year. On a standard 1257L code the payroll gives you a twelfth of the £12,570 Personal Allowance for the month, £1,047.50, whether you worked the whole month or half of it, and National Insurance is assessed on that pay period alone against the monthly primary threshold of £1,048. That is why a small part month often comes with almost no deduction at all, and why the tax on your second full month looks higher than you expected: the allowance you did not use in month one is not lost, it is carried forward and evens out over the year.
Leavers, and the month you are paid for the last time
The same three methods apply in reverse when you leave, and your final payslip may also carry pay in lieu of untaken holiday, which is taxable pay like any other. Two things to check on it: that the part month uses the same method your employer used when you joined, and that any holiday balance is settled at the same daily rate the contract states. If you leave early in the tax year, the cumulative allowance means your final pay can be taxed lightly or even produce a refund, because PAYE has been spreading a full year's allowance across months you will not now work.
Questions people ask about part month salary calculator uk
Which part month method is my employer allowed to use?
Any of them, provided the contract does not say otherwise and the result is not below the National Minimum Wage for the hours worked. There is no statutory formula for a part month of salaried pay, which is the whole reason the three answers differ.
How do I check the figure on my first payslip?
Work out all three. Calendar days is salary divided by 365 times days employed; working days is salary divided by 12 times days worked over working days in the month; the 260th method is salary divided by 260 times days worked. Your payslip should match one of them to the penny.
Why was almost nothing deducted from my first part month?
Because the allowances are monthly, not proportional to the days you worked. A month's worth of Personal Allowance and the monthly National Insurance threshold are set against a part month's pay, so a small first payslip can fall almost entirely inside them.
Does a part month affect my annual take-home?
Yes, because you were paid for part of the year. On £30,000 a full year takes home £25,119.60; a year in which you started on 14 September is a smaller gross and, because the Personal Allowance is a fixed sum rather than a rate, a smaller effective deduction rate as well.