The Church asks for the kind and number of mortal sins; venial sins are good to mention but not strictly required. The bare-minimum form is short. Honesty without over-precision is the goal — say what is necessary, do not perform.

Catholic teaching distinguishes sharply between mortal and venial sins (CCC §§1854-1864). A mortal sin is grave matter committed with full knowledge and deliberate consent; it severs the relationship with God and must be confessed by kind and by number before receiving Holy Communion. A venial sin is the same relationship wounded but not severed; confession of venial sins is salutary and strongly encouraged but not strictly required for absolution.

"By kind and by number" means: name what the sin was (its kind: theft, calumny, missing Sunday Mass) and how many times (its number: once, three times, or for habitual sins an honest estimate — "about once a week for the past two months"). You do not need to describe circumstances unless they change the kind of sin. You do not need to identify other people involved. You do not need to perform a literary set-piece.

The bare-minimum form of a Catholic Confession is short. "Bless me, Father, for I have sinned. It has been [time] since my last Confession. These are my sins: [list of mortal sins by kind and number; venial sins in summary if desired]. I am sorry for these and all the sins of my past life." That is enough. The priest will ask follow-up questions if he needs them. He will give a penance. You make an Act of Contrition. He absolves.

What about over-precision? Scrupulous souls — see A6.04 — often try to describe each sin with such forensic detail that the confessor cannot hear what is being said for the cataloguing. This is not honesty. It is a self-protective evasion: if I describe it precisely enough, I will have done my part and the priest will know I am taking it seriously. The opposite spirit is correct. Say what is necessary. Stop. Trust the priest, and through him trust Christ, to hear what is being said.

What about embarrassing sins? The classical pastoral counsel is unchanged: tell them first. The embarrassment is its own penance, and confessing the embarrassing sin first is an act of trust that breaks the enemy's grip on it. A sin you cannot bring yourself to confess is a sin the enemy is keeping leverage on. Confessing it, even badly, breaks the leverage.

What about sins you cannot remember? You are required to confess all remembered mortal sins. If a mortal sin is genuinely forgotten and surfaces later, it should be confessed at the next opportunity — but it was already forgiven in the previous absolution under the general intention to confess all grave sin. God is not waiting to catch you out on a forgotten sin.

Finally: do not confess temptations. A temptation that was resisted is not a sin; it is a victory. Confess only what you consented to.