How to calculate holiday entitlement when working days change during the year

If an employee changes the number of days they work part-way through the holiday year, their holiday entitlement may also need to change.

For most businesses, the holiday year runs from 1 January to 31 December.

The easiest approach is to split the year into two periods:

Entitlement before the change + entitlement after the change = total holiday entitlement for the year

Example: changing from 5 days to 3 days per week

An employee:

• Works 5 days per week from January to August

• Changes to 3 days per week from 1 September

• Normally receives 28 days' holiday per year (including bank holidays) when working 5 days per week

January to August

They work their original pattern for 8 months:

• 28 × 8 ÷ 12 = 18.7 days

September to December

First, work out their annual entitlement based on working 3 days per week:

• 28 × 3 ÷ 5 = 16.8 days

They work this pattern for 4 months:

• 16.8 × 4 ÷ 12 = 5.6 days

Total entitlement

• 18.7 + 5.6 = 24.3 days

Their total holiday entitlement for the year would therefore be 24.3 days.

What does the 12 mean?

The 12 simply represents the 12 months in the holiday year.

For example: 28 × 8 ÷ 12

means:

• 28 = full annual holiday entitlement

• 8 = number of months worked on that working pattern

• 12 = number of months in the full holiday year

This works out how much holiday applies to that part of the year.

What if the working pattern changes part-way through a month?

If the change happens on a specific date, rather than at the beginning of a month, you can use the exact number of calendar days instead, dividing by 365 (or 366 in a leap year).

For example, an employee:

• Works 5 days per week from 1 January to 7 September

• Changes to 3 days per week from 8 September to 31 December

• Has a full-time entitlement of 22 days plus bank holidays (the calculations below cover the 22 days only)

There are 250 calendar days from 1 January to 7 September:

• 22 × 250 ÷ 365 = 15.1 days

Their annual entitlement on a 3-day week is:

• 22 × 3 ÷ 5 = 13.2 days

There are 115 calendar days from 8 September to 31 December:

• 13.2 × 115 ÷ 365 = 4.2 days

Total entitlement:

• 15.1 + 4.2 = 19.3 days

What happens to holiday already taken?

You do not start the employee's holiday entitlement again when their working pattern changes.

Instead:

1. Calculate their new total entitlement for the whole year.

2. Deduct any holiday they have already taken.

For example, if their new total entitlement is 19.3 days and they have already taken 8 days:

• 19.3 − 8 = 11.3 days remaining

Should holiday be recorded in days or hours?

If the employee's working hours also change, it may be easier to manage their holiday entitlement in hours.

This is particularly useful where a working day before the change is a different length from a working day afterwards.

Remember the statutory minimum

UK employees are normally entitled to at least 5.6 weeks' paid holiday each year.

For example:

• 5 days per week = 28 days

• 4 days per week = 22.4 days

• 3 days per week = 16.8 days

Bank holidays can be included within this entitlement.

Which calculation should I use?

Keep it simple:

• Change on the first of a month? Use the monthly calculation.

• Change part-way through a month? Use the calendar-day calculation.

In both cases, calculate the entitlement for each working pattern separately and then add the two figures together.

--

This article is intended as general guidance only and should not be treated as legal advice. Holiday entitlement can vary depending on an employee’s contract, working pattern and individual circumstances. If you are unsure how the rules apply in a particular case, you should take appropriate legal or HR advice before making any changes to an employee’s entitlement.