It is only if you forget to mention it at all, that you have to go back and confess it later - and only in the case of a mortal sin.
Indeed, because it is the sin(s), their content, that is essential to the matter of the sacrament, not the number of their occasion.
Hence, the penitent, who in confession willfully conceals a mortal sin, derives no benefit whatever; on the contrary, he makes void the sacrament and thereby incurs the guilt of sacrilege. If, however, the sin be omitted, not through any fault of the penitent, but through forgetfulness, it is forgiven indirectly; but it [the sin] *[not a correction of the number of occasions] *must be declared at the next confession and thus submitted to the power of the keys.
newadvent.org/cathen/11618c.htm
Yes, which is why everyone keeps on having to correct you, so that the new people are not led astray into the fear and doubt of scrupulosity.
Indeed.
Again, every sacrament requires essential matter and essential form to be valid.
Necessary matter of this sacrament =
the mortal sins (their content, not their number)
**Necessary form of this sacrament **=
the granting of absolution
The
rubric of the sacrament can be found in a variety of Catholic sources, and begins with the Sign of the Cross, then the self-accusation formula (for example,“Bless me, Father, for I have sinned” is a standard way to begin) as well as length of time since last confession. Then the enumeration of serious sins, usually the most serious first. Normally, number or frequency is part of the rubric.
Jimmy Akin is not an ordained Roman Catholic priest. Usually he has to look up information, and is focused on technicalities. The priests in the confessionals know what the essential matter and form are. If the number of occasions are not mentioned, and the priest does not introduce a question about that, he is judging that it is not important (essential), as he knows what constitutes the validity of the sacrament. He cares about sorrow (contrition) because the Church herself, and Jesus Christ himself, consider that the most essential aspect of the penitent’s preparation – because sorrow signifies understanding of Truth, sorrow invites Mercy, sorrow is a catalyst for change (“firm purpose of amendment”) and sorrow prepares the soul for the sanctifying grace of the sacrament.
If a priest is concerned about the gravity of a particular sin, he is much more likely to inquire of the penitent, “Do you realize the seriousness (or danger) of this sin?” than he is likely to ask, “Well how many times did you do that?” As reported on more than one thread, by several CAF posters, and recently so (and we all have our confessions heard, probably, by different priests), our confessors never ask number of times, even for serious sins. Their understanding trumps anything Jimmy Akin could assert, or any interpretation of the technical “lists” that Jimmy Akin provides. I have two confessors, both of whom are the pinnacle of traditionalism and did not just graduate from seminary (let alone from a conversion process).
It is important to add that rubrics vary. Just as number of sin occasions is not essential to matter and form, neither is the particular confessional formula. Again, I prefer (and my most traditional confessor prefers) the very traditional format, including absolution in Latin. However, many experienced priests use, or accept, formulas and even Acts of Contrition that are variations of the standard or traditional formula. That also does not invalidate the confession, because that belongs to rubric, not to matter & form. Some confessors even prefer the pentitent to say their Act of Contrition privately afterward, outside the confessional.