In customer relationships, the invoice represents the usual conclusion of a transaction between manufacturer and buyer. Through intentional design, the invoice can serve as an innovative marketing tool to achieve business objectives such as increasing customer loyalty or reducing complaint volume. Andreas Aholt first identifies worthwhile design options by summarizing existing insights from marketing research and linking them with his qualitative research. The latter is based on focus groups with consumers as well as a large-scale expert survey with company representatives. In several empirical studies, he subsequently demonstrates the effectiveness of individual design elements. The presented quantitative studies combine classic methods such as experiments and surveys.