I don't see where it says that.
For instance, "1456 Confession to a priest is an essential part of the sacrament of Penance."
Does the Roman Catholic Church teach that it is possible to have a sin forgiven apart from the sacrament of Penance?
In other words, does the Roman Catholic Church teach that it is possible for a truly penitant person to pray directly to God (without any priest administering any sacrament), and confess his or sin directly to God, ask God for forgiveness?
Does the Roman Catholic Church teach that if such a person prays directly to God (with no priest and without any sacrament) that God will forgive the sin that the penitant person confesses and asks forgivenss for?