Many Protestants mistaking claim that the Catholic Church teaches that one can receive an Indulgence for the remission of sins.
The definition of indulgences presupposes that forgiveness has already taken place; they deal only with punishments left after sins have been forgiven.
CCC 1471 An indulgence is a remission before God of the temporal punishment due to sins whose guilt has already been forgiven, which the faithful Christian who is duly disposed gains under certain prescribed conditions through the action of the Church which, as the minister of redemption, dispenses and applies with authority the treasury of the satisfactions of Christ and the saints.
To acquire a plenary indulgence, it is necessary to perform the work to which the indulgence is attached and to fulfill three conditions: sacramental confession, Eucharistic Communion, and prayer for the intentions of the supreme pontiff. It is further required that all attachment to sin, even to venial sin, be absent. If this disposition is in any way less than complete, or if the prescribed three conditions are not fulfilled, the indulgence will be only partial. (Paul VI, apostolic constitution, Indulgentiarum doctrina )