When can a referee show a red card or yellow card during a match?

The correct understanding of when a referee can show a red or yellow card is that it can only occur after the match has officially started. Cards are disciplinary measures that are used to signify cautions or send-offs for misconduct that occurs during the active play of a match.

Showing a card before the match starts or during half-time does not pertain to any actions taken on the field since the game is not in progress at those times. Although referees may talk to players before the match about potential disciplinary actions or behavior expectations, the actual showing of a card relating to an infringement only takes place while the game is being played. Therefore, recognizing that cards are tools meant to manage conduct during active play underscores why they can only be issued once the match has begun.