A reader writes:
I am aware that if one goes to confession and supplies the requisite contrition, then all sins which the person committed are absolved–provided that the person does not intentionally conceal any mortal sins.
Correct.
Also, I have been told by several priests that this means that if one remembers a mortal sin after confession, they should know that they are forgiven for it so long as they mention it the next time they go to confession.
Correct, though this should be formulated a little differently. You are forgiven if you meant to confess all your mortal sins and just forgot one. Having been forgiven of the one you forgot, you are still obligated to confess it the next time you go to confession. It’s not that your forgiveness of it is conditional on you adopting the intention to confess it next time. That sin has already been forgiven. It’s that you incur a new sin if you refuse to adopt the intention of confessing it.
Now I remember that you did a similar blog topic about this fairly recently, but my question is one that I don’t think you dealt with in that blog.
My question is after one has remembered the mortal sin, how soon is one required to seek out confession? For example, if I go to confession and mention everything I can bring to mind, but immediately afterward remember a mortal sin, must I go to confession to mention the mortal sin as soon as possible? Or could I just wait 2 weeks, a month, etc., until I feel like going to confession? And can I receive communion in the meanwhile?
Since you are not in a state of mortal sin, you can receive Communion prior to your next confession.
As to how long you can wait before the next confession, the fact that you have an already-forgiven-but-not-yet-confessed sin does not create an obligation to go at any particular time, though one might suggest that one should go before one is likely to forget the mortal sin that needs to be mentioned.
Consequently, church law does not require one to go within any particular time frame, other than the obligation to confess one’s mortal sins at least once a year. It would be arguable whether this law applies to forgiven-but-unconfessed sins or not. The purpose is clearly to deal with mortal sins that haven’t been forgiven, so in the absence of clarification that it applies to those that have as well, it would seem that liberty would be presumed on the grounds of it being doubtful whether the law applies to this case (canon 14).
Now, there is language in some Church documents about going to confession "as soon as possible," but this is connected with a different situation, which is described in canon 916:
A person who is conscious of grave sin is
not to celebrate Mass or receive the body of the Lord without previous
sacramental confession unless there is a grave reason and there is no
opportunity to confess; in this case the person is to remember the obligation
to make an act of perfect contrition which includes the resolution of
confessing as soon as possible.
What this canon is talking about is a person who has not been to confession and who can’t go, not a person who has been and just forgot a sin. That person needs to make an act of perfect contrition in order to get back into a state of grace and thus able to take Communion, and making an act of perfect contrition includes the will to go to confession when it is possible (and reasonable) to do so.
The Code formulates this in terms of going "as soon as possible," but what it means by this is as soon as it is possible and reasonable for a person to go. The Church does not expect you to do unreasonable things just to be able to go a sooner. (E.g., driving recklessly in order to get to the church a little faster or demanding that the priest get out of bed to hear your confession.) There is an unstated reasonableness condition in this canon.
This may be where you got the idea about needing to go "as soon as possible," but it does not apply to your case. It deals with those who have an unforgiven sin and can’t go to confession before Communion, not those who went to confession and got forgiven but forgot to mention something.
Your sins already have been remitted by the sacrament of confession. You just forgot something.
This kind of situation happens all the time, and if there were a requirement to go to confession within a particular timeframe, it would be on the books.

