Venial sins can be, but mortal sins can only be forgiven through the sacrament of penance. Although it is recommended to confess venial sins in the sacrament of penance as well.
Roman Catholic AnswerNo, not normally. If you are referring to a good confession in which you, perhaps, honestly forgot a sin, then, yes, in that instance, the sin would be forgiven IF you mention it during your next confession, and tell the priest that you honestly forgot it last time. But if you are asking if your sins are forgiven if you just neglect to go to confession and tell all of them, then no. Jesus set up confession as the normal way of having your sins forgiven, and you must abide by that.
Roman Catholic AnswerThere is no such thing as a "grant from the Catholic Church forgiving sins"; it sounds like you are asking about indulgences, as there is a common misconception of many protestants that indulgences are a grant to forgive sins, I don't know where that came from but it's not true. Indulgences can be earned by someone who is in a state of grace, in other words, someone who has already had their sins forgiven by God in the confessional, not otherwise. There is no other normal way, on this earth, to have your sins forgiven then in the confessional, and that is most definitely not an indulgence.
An indulgence is a remission of the temporal punishment for sins already forgiven.
G. K. Chesterton
Roman Catholic AnswerFor the same reason they confessed their sins in the first century, or in this century: to be forgiven for those sins, because Jesus told them to.
.Catholic AnswerYes, that was one of the problems.
Sins that are confessed to a priest and proper penance was observed, such sins are forgiven and not accountable and need not be confessed again.
All sins can be forgiven in may ways because God can do all things
When you confess your sins to a priest, all of your sins are forgiven and you basically start of with a clean slate. It is the stepping stone needed for all other Sacraments other than Baptism.
Mortal sins can only be forgiven in the sacrament of penance or with an act of perfect contrition with the resolve to go to confession as soon as possible. Venial sins can be forgiven with an act of imperfect or perfect contrition, reception of the Holy Eucharist, use of a sacramental, after death.
Of course, the only sins which cannot be forgiven are the unforgivable sin which is the sin against Hope (the second of the Cardinal Virtues). The sins against hope which cannot be forgiven are presumption and despair.The former is akin to the Protestant theory that once you are "saved" you cannot do anything to lose your salvation. That is presumption and is unforgivable as you don't think you need forgiveness.The latter, despair, is unforgivable as you don't think you can be forgiven for whatever reason: you think you have committed too many sins, or too horrible a sin, or whatever.The sins against hope cannot be forgiven for the simple reason that you cannot be contrite and ASK for forgiveness. God will forgive ANYTHING as long as we repent of it - which is not just being sorry for it, but trying not to do it again.Sins which we have not yet done cannot be forgiven until AFTER we do them, and repent of them. But all mortal sins can be forgiven as long as we confess them and repent. It is only when we are not contrite and repentant that we cannot be forgiven.
I don't quite know what you are asking. If you are asking whether or not it is sinful for a Catholic to go to Confession: it is not. Confession was instituted by Christ for our sanctification.