Standards for carry-over and cash-ins of vacation days

Can employers force employees to take vacation days rather than carry them over or cash them in?
By Tim Mitchell
|Canadian Employment Law Today

Question:

If vacation accrued during one year has not been used, does it have to be carried over to the next year or can the employer forfeit it? If carried over, is there a maximum amount of vacation time an employee can carry over from one year to the next? Can the employer reject a request to forego vacation time and cash it in? If the employer’s HR policy does not allow the vacation time to be cashed in, is there any alternative for the employee other than using it as leave?