substitution (NF)
 

I had this play earlier in the season, haven't gotten around to posting it until now...just wondering if I got it right:

Ball on the far hash. B12 comes off the bench on my side. He gets to the near hashes. He does not communicate with players on the field, no one moves to come off as he comes on. The bench realized B12 is indeed the 12th man on the field, they yell for him to come back. He almost gets to the numbers before the snap. Play happens (to the other side of the field) as he continues his run the bench. He was always on his side of the NZ. I flagged for live ball illegal substitution. Correct? (Do you need any other information about the situation?)

And, in case you are wondering, we enforced from the previous spot, which I know is incorrect in a non-player foul.

Canadian Ruling
 

CANADIAN RULING:

I will adjust the situation and assign B12 -> B13, since we allow 12 players per team∙play.

This generally will not be a foul. If a player communicates with an on-field teammate, then he must stay in for that play. That means that someone must leave. If nobody leaves, then you have IS/Too Many Men. If he doesn't stay, then you have IS.

It is also a requirement that no opponent was confused by this player's actions. The fact that the play went to the other side also further strengthens the fact that this is not a foul. Had the play been to the same side as B13 little jog to the field and back to the sideline, then the official's judgment is used. I'm still supporting a no flag in this case, as it seems by the OP that the player exited the field well before the ball came to near where he was.

You were right IS Pre spot for enforcement.

You were correct in calling it IS, and correct in it being a PS enforcement.