[AtlUmpSteve]

No direct penalty is currently available for an unreported sub after a pitch is thrown. You legalize the substitution and announce the sub when it happens. There is a penalty for an unreported batter if appealed before the next pitch, or for an unreported defensive sub making a play if appealed before the next pitch.

I say direct penalty, because I would consider a matter of game management to address the head coach that all subs must be reported into the game, and that I would consider it a matter of intentional unsportsmanlike conduct by the head coach if he/she continued to enter unreported subs. I think we all know the penalty for an intentional unsportsmanlike act.