Employers must respond to changes in employees’ work patterns or standard hours – employers need to be aware of any permanent or temporary changes. The minimum annual leave entitlement is 4 weeks per year on anniversary and the agreed standard hours at that time will dictate how much leave is due on their anniversary.
For an employee that reduces hours part way through the anniversary year, you can hold the balance accrued on the higher hours and use this to pay an average hours for a days leave which can be agreed by the employee and employer.