Underpayment and wage theft are common across Australian industry; for highly vulnerable employees who are commonly deprived of their legal entitlements to an extent that violates Australian labour laws. This thesis seeks to explain the sources of employee vulnerability and why some employers are driven to engage in these illegal activities. The analysis is based on 119 court cases and this study provides a level of detail that assists the identification of nine groups of vulnerable employees; three situational and structural factors that contribute to employee vulnerability and five drivers of employer non-compliance.