TESIs POSTÍTULO DE ECONOMÍA Y FINANZAS PARA ABOGADOS / La ley 20.780 introdujo un nuevo impuesto a las fuentes móviles de contaminación, que grava la compraventa de vehículos nuevos. Sí bien se declaró que se trataba de un impuesto verde, es decir, que fue establecido para desincentivar las conductas contaminantes, lo cierto es que no lo ha logrado efectivamente y solo ha generado un aumento en la recaudación fiscal. Se analizará el concepto de impuesto verde en abstracto, la historia fidedigna de la modificación legal y los datos del mercado automotor. Law 20,780 introduced a new tax on movable sources of pollution, which levies the purchase of new vehicles. Despite having being declared as a green tax, that is, having being established to discourage polluting behaviors, this has not been successfully achieved, and has only increase the tax collection. It will be further analyzed the abstract concept of green tax, the history of the legal amendment and data from the vehicle market. / Law 20,780 introduced a new tax on movable sources of pollution, which levies the purchase of new vehicles. Despite having being declared as a green tax, that is, having being established to discourage polluting behaviors, this has not been successfully achieved, and has only increase the tax collection. It will be further analyzed the abstract concept of green tax, the history of the legal amendment and data from the vehicle market.