Yes, penalties can be imposed after the completion of a round. Golf is a game of honor, and players are expected to report any rule violations, including those they may have discovered after the round. If a player realizes that they have breached a rule during the course of play, but only after completing the round, they should inform the tournament committee as soon as possible. In some cases, the penalty may affect the player's score, standings, or even disqualification from the tournament.