Lohn Vom Dritten: Zuwendungen Dritter an Arbeitnehmer Und Ihre Arbeits-, Steuer- Und Sozialversicherungsrechtliche Behandlung

Today employees do not only receive their wage just from their employers: International corporate groups distribute group-wide bonuses, sales employees collect producer premiums and service employees are often existentially dependent on tips. In all these cases, employees receive contributions from third parties to whom they are not contractually bound. How have those third-party-contributions to be treated legally in terms of labour, tax, social security law?