Is it obligatory to mention forgotten sins at confession?

[Soler]

I am aware that it is a common practice for people to mention at confession mortal sins that they forgot to confess at their last confession. My question: Is this practice obligatory? To extend the question: Must we, in making our examination of conscience, attempt to recall sins we forgot to confess as well as those we have recently committed? And what about sins which were forgotten at a confession prior to one’s last confession? I am fully aware that these problems could be largely solved by going to confession more often. If you suspect scrupulosity, I have quite a legalistic mind, which can cause me to be somewhat scrupulous at times and a callous rationalizer at others. Thank you.

[Michelle Arnold]

Originally Posted by Soler

I am aware that it is a common practice for people to mention at confession mortal sins that they forgot to confess at their last confession. My question: Is this practice obligatory?

Yes.

Originally Posted by Soler

To extend the question: Must we, in making our examination of conscience, attempt to recall sins we forgot to confess as well as those we have recently committed?

We should make a good-faith effort to make a good confession of all mortal sins that have not yet been confessed.

Originally Posted by Soler

And what about sins which were forgotten at a confession prior to one’s last confession?

Just consider them "forgotten" sins; if they were mortal sins, confess them.

Originally Posted by Soler

I am fully aware that these problems could be largely solved by going to confession more often. If you suspect scrupulosity, I have quite a legalistic mind, which can cause me to be somewhat scrupulous at times and a callous rationalizer at others. Thank you.

I like to end my confessions with "For all the sins of my past life, and for any that I've forgotten, I am truly sorry." This doesn't get you "off the hook" if you later remember a mortal sin you forgot to confess -- you still must confess it at your next confession -- but I find saying this helps me in dealing with my own scrupulosity over "forgotten" sins.