The UK holiday law most leave trackers 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 (Harpur Trust v Brazel)
Since the Supreme Court's 2022 ruling in Harpur Trust v Brazel, holiday entitlement for irregular-hours and zero-hours workers can't simply be pro-rated against a full-time year — it has to accrue against hours actually worked. The commonly-used shortcut is 12.07% of hours worked (52 weeks minus 5.6 weeks' statutory leave, expressed as a percentage), applied pay-period by pay-period. Get it wrong and you're either underpaying statutory entitlement — a real legal exposure — or overpaying it indefinitely because nobody's tracking hours worked against the 104-week reference period the rules require.
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(10)/(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: the Working Time Regulations protect it on its own 18-month carry-over window, regardless of your normal policy. Most leave trackers either don't distinguish the two at all, or expect an admin to remember to flag it manually — which is exactly the kind of thing that gets missed until an employment tribunal asks about it.
Otium One tracks this leave separately the moment it's booked, so the 18-month window is enforced automatically instead of depending on someone remembering the exception.
A typical leave tracker vs. Otium One
| Rule | Typical leave tracker | Otium One |
|---|---|---|
| Zero-hours & irregular-hours accrual | A manual spreadsheet workaround, or left for an admin to estimate. | 12.07% accrual calculated automatically, on the approach set out in Harpur Trust v Brazel, with hours-worked records kept for the statutory 104-week reference period. |
| Carry-over blocked by sickness or family leave | Treated the same as ordinary carry-over, if it's handled at all. | Tracked separately under WTR reg 13(10)/(13): protected leave carries over on 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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