111. Match Structure
Three is the default number of games in a Magic match, and tournament organizers must allow three games per match. If a tournament organizer chooses, he or she may run single-elimination final rounds as best three games out of five. This choice must be announced before the tournament begins. Match results, not individual game results, are reported to the DCI for the purpose of inclusion in worldwide ratings and rankings.
Drawn games (games without a winner) do not count towards one of the games in a match. The match should continue until one player has won the majority of games as long as match time allows.