Most of the year, working out holiday is simple. Everyone has their allowance, they book time off, the balance ticks down. It is the edges of the leave year that catch people out: someone joins in March, someone hands in their notice in September, or someone changes their hours part way through the year. In each of these cases you are no longer dividing a full year's entitlement evenly, you are working out a fair slice of it. Here is how to do that for mid-year starters and leavers, and for the trickier case of changing hours, without reaching for a spreadsheet you do not quite trust.
Start with the full-year figure
Before you can work out a partial year, you need the full-year number. By law, almost every worker in the UK gets 5.6 weeks of paid holiday a year. For someone on a standard five-day week that comes to 28 days, and 28 days is the statutory cap even for people who work six days a week. Bank holidays can sit inside those 28 days or be granted on top, depending on the contract.
If your business offers more than the legal minimum, say 25 days plus bank holidays, use your own figure as the full-year total. Every calculation below is just a proportion of that number.
Holiday for someone who joins mid-year
When a full-time employee starts part way through the leave year, they are entitled to the portion of the year they will actually work. The quick version: someone who starts exactly halfway through gets half the full-year allowance.
In practice the first year has a specific accrual rule. Leave builds up at one-twelfth of the annual entitlement for each month of the leave year, rounded up to the nearest half day. GOV.UK gives the example of a five-day worker on a leave year that starts on 1 January: someone who starts on 13 January has accrued 2.5 days by the end of January, because 28 divided by 12 is 2.33, rounded up.
A worked example. Priya joins on 1 April, your leave year runs January to December, and full-time entitlement is 28 days. She will work 9 of the 12 months, so she accrues nine twelfths of 28, which is 21 days for her first, partial year. From the following January she gets the full 28.
You can check any of this with our holiday entitlement calculator, which takes the leave year, the start date and the working pattern and returns the pro-rated figure to the nearest half day.
Holiday for someone who leaves mid-year
For a leaver, you work out how much they have accrued up to their last day, then compare it with how much they have already taken. Accrual is pro-rated to the part of the leave year they have worked, so someone who leaves exactly halfway through a 28-day year has accrued 14 days.
If they have taken less than they have accrued, you owe them the difference as pay in their final wages. If they have taken more, you can usually recover the overpayment from their final pay, but only where their contract allows it. We covered the payment side of this, including how to handle someone who has taken more than they have earned, in what happens to unused holiday when someone leaves your business.
A worked example. Tom's last day is 30 September, your leave year is January to December, and full-time entitlement is 28 days. He has worked roughly three quarters of the year, so he has accrued about 21 days. He has taken 18, so you owe him 3 days of pay on top of his final salary.
Our remaining leave calculator does this exact sum for you: enter the allowance, the days taken and the last working day, and it returns the balance to pay out or reclaim.
When someone changes their hours part way through the year
This is the one that causes the most head scratching, and it sits behind a lot of "holiday calculator changing hours part way through year" searches. The key principle, set out by ACAS, is that you recalculate from the date the change takes effect, and the change does not touch any holiday already accrued before it. You do not rework the whole year at the new rate.
The method is to split the leave year into portions, work out the entitlement for each portion based on the pattern worked during it, then add them together. ACAS uses the example of Pat, who drops from 40 hours a week to 20 hours a week three months into the leave year. Pat's entitlement is worked out as three months at the full-time rate plus nine months at the reduced rate.
There is a wrinkle worth watching. It is unlikely anyone will have taken exactly the share of holiday they accrued at the old rate before the change. If Pat accrued seven days in the full-time portion but had only taken three, those remaining four full-time days carry forward and get taken on the new, reduced pattern. Keep the accrued and the taken figures separate so nothing gets lost.
Because a change of hours usually means moving to a part-time or irregular pattern, the detail of calculating the new portion follows the part-time rules. Our guide to calculating holiday for part-time staff walks through that method with examples.
Keep the running total somewhere you can find it
None of these calculations are hard on their own. What makes them painful is doing them by hand, in a spreadsheet, while also remembering who has booked what and when. The full-year figure, the pro-rated figure, what has been taken and what remains: keep all four somewhere clear, because a number scribbled on a contract is not something you will be able to defend six months later.
Absently is built for small UK teams of full-time staff, and it does the mid-year maths for you. Add a new starter with their start date and it pro-rates their first-year entitlement automatically, then tracks every day booked so the balance is always right there. When someone hands in their notice, you can see at a glance what they have accrued and what they have taken, which is exactly the figure you need for their final pay.
It is 1 pound per person per month, with a 30-day free trial and no card needed to start. If you are tired of rebuilding the same formula every time someone joins or leaves, start your free trial and let the running total look after itself.