The Martyrdom of St. Demetrios
The Monastery of Megisti Lavra
Mount Athos
When is a Catholic obliged to confess his serious sins? How often should one go to confession?
Upon reaching the age of reason, a Catholic is obliged to confess his serious sins. The Church urgently advises the faithful to do this at least once a year. At any rate one must go to confession before receiving Holy Communion if one has committed a serious sin.
By "the age of reason", the Church means the age at which one has arrived at the use of reason and has learned to distinguish between good and bad.
Can I make a confession even if I have not committed any serious sins?
Confession is a great gift of healing that brings about closer union with the Lord, even if, strictly speaking, you do not have to go to confession.
In Taizé, at Catholic conferences, at World Youth Day celebrations - everywhere, you see young people being reconciled with God. Christians who take seriously their decision to follow Jesus seek the joy that comes from a radical new beginning with God. Even the saints went to confession regularly, if possible. They needed it in order to grow in humility and charity, so as to allow themselves to be touched by God's healing light even in the inmost recesses of their souls. (YOUCAT questions 234-235)
Dig Deeper: CCC section (1457-1458) and other references here.