We do receive enquiries from members who want to ensure whether they are entitled to refuse an instruction from their employer if the task is not in their job description and/or in line with their grading.
In terms of Clause 3.9 (2) of the MIBCO Main Collective Agreement you might be eligible for a higher wage on the days that you are required to perform a higher grade task. This provision provides that in the event that you are required to do work that does not fall within your scope, which you are skilled and/or qualified to do, accumulatively for more than 60 minutes in any one day you should be paid on that grade for the day.
Bear in mind that should you be tasked with work on the same/or lower grade than what you are contractually bound to, your salary/wage shall not be less than agreed.
In a Nutshell: It is permissible to perform duties above your current grading and to be paid that grade on that day, provided that you are skilled and/or qualified and do so for longer than sixty (60) minutes accumulatively.