Under the Fair Work Act 2009 (Cth) (FWA), an employee can take sick leave if they are not fit for duties because of personal illness or injury, but the employee must comply with the notice and evidence requirements in s107 of the FWA.
An employee must provide the employer with notice “as soon as practicable”, which can be after the sick leave has begun, and they should also advise how long they will be absent. An employer can ask the employee to provide evidence that the employee is unfit for their duties and should be cautious about rejecting a medical certificate presented by an employee from a qualified medical practitioner. Employers can only reject the validity of the certificate in the “most unusual and exceptional circumstances”.
In Anderson v Crown Melbourne Pty Ltd  FMCA 152, the employee presented a medical certificate to cover his absence when he attended an AFL match in Perth. The employer was aware the travel from Melbourne to Perth had been booked and that the employee had obtained tickets to the match. The employee told his workmates the employer was not entitled to challenge the medical certificate he obtained so he could go to the football.
After his dismissal, the employee filed unfair dismissal proceedings and the Commission dismissed the case because it found the medical certificate was invalid and the employee’s absence amounted to misconduct.
Rejecting medical evidence and dismissing an employee may expose the employer to claims of bullying, adverse action, discrimination or workers’ compensation, and they may be ordered to reinstate employees and pay compensation.
An employer should also consider the terms of the employee’s employment contract or award when an employee takes leave. As well as the FWA, employers may need to consider other legislation including the Workers’ Compensation and Rehabilitation Act 2003 (Qld) and the Industrial Relations Act 1999 (Qld).
Where there is any doubt, it is wise to consult your lawyers for guidance before you act.