Private companies are explicitly and implicitly, directly and indirectly, involved at all stages of the migration process. This delegation of migration control functions to private actors is largely unregulated and the multi-layered policy implications are not well understood. The lines of responsibility and accountability, but also liability, for decisions being made and for force used are not always clear and this most seriously affects vulnerable migrants and potential migrants. This delegation is occurring in some form in all global regions. International agreements relating to migration do not take this privatisation into account and international discussions about the obligations of private companies do not consider the Migration Business directly. This survey article presents the situation and argues that informed international policy debate is needed in this area.