In the Catholic Church prior to the Reformation, indulgences were ways in which a sinner could reduce his punishment. Indulgences usually involved the performance of some good deed or the saying of a specific prayer. They were also meant to reduce the punishment that a person would receive in Purgatory.
Indulgences became problematic by the Late Middle Ages, as they had become seriously commercialized. Indulgences were one of the main complaints from Protestant theologians. However, they remained common within the Catholic Church until the 20th century.