The general protections under the Fair Work Act prohibit, amongst other things, the taking of adverse action for a prohibited reason.
There has been some judicial controversy about what is meant by the expression “adverse action” and here is an extract from a recent Federal Circuit Court case which explains the concept.
“The expression “injures the employee in his or her employment” refers to a deprivation of one of the more immediate practical incidents of an employee’s employment, such as loss of pay or reduction in rank. The phrase extends to injury of any compensable kind, a legal injury, or an adverse effect on an existing legal right.
 Patrick Stevedores Operations No.2 Pty Ltd v Maritime Union of Australia (No.3) (1998) 195 CLR 1 (at ); Australian and International Pilots Association v Qantas Airways Ltd  FCA 1441 (at -) and Unsworth v Tristar Steering and Suspension Australia Limited (2008) 216 FCR 122 (at )
For there to be adverse action, the employee, individually speaking, must be in a worse situation after the relevant conduct than he was before it and the deterioration in his position must have been caused by the employer’s conduct. The employer’s acts must in fact amount to a prejudicial alteration which is real and substantial rather than merely possible or hypothetical.
 Community and Public Sector Union v Telstra Corporation Ltd (2001) 107 FCR 93 (at -); Finance Sector Union of Australia v Commonwealth Bank of Australia Ltd (2005) 147 FCR 158 (at -)
 Community and Public Sector Union v Telstra Corporation Ltd (2001) 107 FCR 93 (at )”
Keenan v Cummins South Pacific Pty Ltd (2018) FCCA 2600 delivered 14 September 2018 per Wilson J