200. How are sins remitted?
(Comp 200) The first and chief sacrament for the forgiveness of sins is Baptism. For those sins committed after Baptism, Christ instituted the sacrament of Reconciliation or Penance through which a baptized person is reconciled with God and with the Church.
(CCC 984) The Creed links "the forgiveness of sins" with its profession of faith in the Holy Spirit, for the risen Christ entrusted to the apostles the power to forgive sins when he gave them the Holy Spirit.
To deepen and explain
(CCC 976) The Apostle's Creed associates faith in the forgiveness of sins not only with faith in the Holy Spirit, but also with faith in the Church and in the communion of saints. It was when he gave the Holy Spirit to his apostles that the risen Christ conferred on them his own divine power to forgive sins: "Receive the Holy Spirit. If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained" (Jn 20:22-23). (Part Two of the catechism will deal explicitly with the forgiveness of sins through Baptism, the sacrament of Penance, and the other sacraments, especially the Eucharist. Here it will suffice to suggest some basic facts briefly.)
(CCC 980) It is through the sacrament of Penance that the baptized can be reconciled with God and with the Church: Penance has rightly been called by the holy Fathers "a laborious kind of baptism." This sacrament of Penance is necessary for salvation for those who have fallen after Baptism, just as Baptism is necessary for salvation for those who have not yet been reborn (Council of Trent (1551): DS 1672; cf. St. Gregory of Nazianzus, Oratio 39, 17: PG 36, 356).