So far, there has been no comprehensive study on the relationship between the concepts of contributions in civil law and tax law. The general part of this work fills this gap. Here, the concepts of contribution, transfer, exchange, and exchange-like transactions are explained. In addition to describing the similarities and differences as well as the relationship between the terms, precise definitions that clearly distinguish them from one another are formulated. In a further part of the work, an in-depth analysis of the case law of the Federal Fiscal Court (BFH) regarding open contributions follows, with particular scrutiny of the corporate law reasoning of the BFH. The author concludes that the so-called exchange-like transactions are only inadequately grounded dogmatically in the current income tax law. He rejects the prevailing exchange theory de lege lata but discusses its legal anchoring de lege ferenda.