CEP services (courier, express and parcel services) currently show a strong growth trend both in Germany and in other European countries such as Poland. As the demand for CEP services increases, so does the consumption of resources and the resulting environmental impact. At the same time, CEP services, with their complex chain of transport and logistics elements, offer a multi-layered potential for reducing adverse environmental effects. This applies both to CEP shipments between companies (business-to-business services) and between private individuals and companies. In a field experiment conducted by the project team of this project in cooperation with a Polish courier service provider, the willingness of companies to voluntarily offset CO2 emissions was investigated.The results of this first field-experimental analysis with mainly corporate customers are now being supplemented by the perspective of end customers. To this end, the researchers are conducting a survey with a representative sample of the Polish population - as final end customers in the value chain. With the help of the survey data, the project team will in particular investigate the willingness to pay for voluntary CO2 offsetting at individual level. These findings on the behaviour of individuals are to reflect the observations on voluntary CO2 offsetting of courier services in the context of Polish business-to-business relations, which have already been made at company level. By the planned extension of the previous project approach, the decision situation of complex supply relationships can thus be extended by a scientifically relevant perspective.