For employees not covered by an Award or Enterprise Agreement (industrial instrument) – your employer, under the Fair Work Act 2009 (Cth) (section 94(5)), can direct you to take you annual leave at a certain time, however, it must be ‘reasonable’.
It would be ‘reasonable’ if for example, you had accrued an excessive amount of annual leave or if the business is being shut down for a period (i.e. during the Christmas/New Year break). What is considered ‘reasonable’ will also depend on the amount of notice you are given as well as the amount of leave you are being directed to take.
For employees covered by an Award or Enterprise Agreement (industrial instrument) – your employer will only be able to direct you to take leave if it is provided for in the industrial instrument.