Holiday pay is not just a payment to employees while on annual leave. Holiday pay implies multiple meanings:
Ordinary weekly pay and Average weekly earnings
An employee on annual leave must get paid more than Ordinary weekly pay and Average weekly earnings.
Holiday pay has to be paid if employees are entitled to be paid holiday pay before starting a period of annual leave, unless employees agree that they are to be paid on the day they would normally be paid if they were not on leave or the employees were terminated from employment.
If you used “pay as you go” holiday pay incorrectly, and employees works for more than 12months, the employee will be entitled 4 weeks paid annual leave, even if they received holiday pay during the first period. It means they get paid twice for annual leave earned in the first year.