Under the German Basic Law (Grundgesetz), non-tax levies – in contrast to levies, which can technically be classified as taxes – interfere with both the fiscal constitution and the constitutional guarantee of equality. Nonetheless, the German Federal Constitutional Court (Bundesverfassungsgericht) has accepted different types of non-tax levies such as fees (Gebühren), contributions (Beiträge) and special levies (Sonderabgaben). Unlike the other forms of nontax levies, a special levy is imposed on a group of chargeable persons as such; from the perspective of the individual, there are no specific reasons for his liability to make payment except his affiliation to that group. Therefore, a special levy raises particular constitutional concerns. According to the established case-law, the following conditions have to be met: The revenue has to be used to finance a specific public purpose which goes beyond mere fundraising; the group of chargeable persons has to be homogenous; there has to be a specific relationship to the objective which is pursued by the collection, that allows to attribute a financial responsibility to that group; finally, the group has to benefit from the objective pursued. These criteria do not provide an adequate response to the constitutional concerns raised by special levies. They are unclear and therefore cannot ensure that their imposition, as the Federal Constitutional Court itself has demanded, remains a rare exemption. An examination of some recent cases reveals, that there are only two situations in which a special levy is constitutionally acceptable: (1) The group of chargeable persons has provoked a specific public measure; a special levy then can be imposed as the financial responsibility of the group follows from the idea of causation. (2) The group of chargeable persons is subject to a specific public measure it clearly and intentionally benefits from; a special levy then can be imposed as the financial responsibility of the group follows from the idea of quid pro quo. This concept clarifies the reasons for a financial responsibility and helps to integrate the special levies into a consistent system of non-tax levies.