Multiple ron
Multiple ron is a case where a player's discarded tile (or a tile added to a kan) has been claimed for a win by more than one player. Most often, this involves the situation of double ron. In rare cases, it can also involve triple ron. The exact handling of the situation depends on the rule variations in use.
Multiple Wins
One variation is to award a win to every player with a winning hand. In this instance, the losing player pays for each winning hand separately.
The exact handling of riichi bets and renchan is subject to further variation. Usually, the riichi bets are awarded to the leftmost player who won (that is, the player whose turn would come next). If the other winning player(s) had declared riichi, they may be allowed to reclaim them, or they may all go to the same player.
Under some rulesets, if oya is one of the multiple winners, this will always result in a renchan. Under others, the deal will rotate unless oya is the leftmost winner.
Atamahane
An alternate common variation, called atamahane is to award a win only to the leftmost player (that is, the player whose turn would come next). All other wins are ignored.
Chombo
If a player declares a false win at the same time as another player declares a real one, the chombo penalty is usually nullified. Some rulesets may, however, retain the full penalty, or provide that a lesser penalty be paid.
Sanchahou
The final variation, applicable only in the case of triple ron, is called sanchahou. If this rule is being used, a triple ron results in an abortive draw and the hand is replayed. The player who was called off of escapes having to pay for three hands.
Under an uncommon rule variation, if a double ron occurs, the final player must reveal their hand to prove that they could not have legally called ron (including due to furiten). If they could have, then the hand is still an abortive draw. This rule is to prevent a player from choosing not to call ron after hearing that two other players have done so.