The UK holiday law employers most often get wrong.
Two rules catch out almost every UK employer with part-time, irregular, or zero-hours staff. Here's what they actually require, and how Otium One calculates them for you instead of leaving it to a spreadsheet.
The 12.07% rule for irregular hours
In Harpur Trust v Brazel (2022), the Supreme Court ruled that part-year workers were due the full 5.6 weeks' holiday, with no pro-rating for the weeks they didn't work. The government changed the law for leave years starting on or after 1 April 2024: irregular-hours and part-year workers now accrue holiday at 12.07% of the hours they work in each pay period (5.6 weeks' leave against the 46.4 weeks left to work in a year). Holiday pay is then based on their average over the last 52 weeks worked, looking back up to 104 weeks. Get it wrong and you're either underpaying statutory entitlement — a real legal exposure — or overpaying it because nobody's tracking the hours worked.
Otium One accrues this automatically per pay period and keeps the hours-worked history the rule depends on, so it's calculated correctly without anyone maintaining a formula.
Statutory carry-over (WTR reg 13)
Ordinary carry-over is whatever policy you set. But leave someone couldn't take because they were off sick, or on maternity/paternity/adoption/shared parental leave, is different, and protected regardless of your normal policy. Leave lost to sickness can be carried over and taken up to 18 months after the end of its leave year; leave lost to family leave must be allowed to carry into the next leave year. Handled by hand, this depends on an admin remembering to flag it — exactly the kind of thing that gets missed until an employment tribunal asks about it.
Otium One works out this protected leave separately every time a leave year closes, and gives both kinds the full 18 months (more than the minimum for family leave), so it's never lost because someone forgot the exception.
By hand vs. Otium One
| Rule | Done by hand | Otium One |
|---|---|---|
| Zero-hours & irregular-hours accrual | A manual spreadsheet workaround, or left for an admin to estimate. | 12.07% accrual calculated automatically each pay period, as the Working Time Regulations require, with leave charged at average hours over the 52-week reference period. |
| Carry-over blocked by sickness or family leave | Treated the same as ordinary carry-over, if it's handled at all. | Worked out separately under WTR reg 13 at each leave-year end: protected leave gets its own 18-month window, independently of your normal carry-over policy. |
| Bank holidays & regional variation | A single UK-wide list, or a manual per-employee adjustment. | Regional bank holidays (England & Wales, Scotland, Northern Ireland) plus your own closure days, factored into every entitlement calculation automatically. |
| Pro-rata on starters, leavers & mid-year changes | Recalculated by hand, or not recalculated until someone notices. | Recalculated correctly the moment a start date, leave date, or working pattern changes. |
Every rule here is included. Nothing to unlock.
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