The full answer

Every NDIS worker — registered or unregistered, employee or contractor — must hold a valid NDIS Worker Screening Check before delivering supports. Each state issues its own clearance through its police-checks unit (DCJ NSW, DHS SA, Blue Card Services QLD, etc.). Cost ranges $0 (volunteers) to ~$120 (paid workers); valid for 5 years. The clearance is portable across states. Working With Children Check is separate and may also be required for child-facing roles.