If you have taken paid personal leave (sick leave) and your employer requests that you provide a medical certificate, then you will need to comply.

The Fair Work Act 2009 (Cth) (FW Act), section 97 allows you to take paid personal/carer’s leave when you are not fit for work because of a personal illness, or personal injury, affecting the employee; or when you need to provide care or support to a member of your immediate family or household, who requires care or support because of a personal illness, or personal injury, affecting the member; or an unexpected emergency affecting the member.