(1) Making Stroke at Wrong Ball. A player must not make a stroke at a wrong ball.

Exception - Ball Moving in Water: There is no penalty if a player makes a stroke at a wrong ball that is moving in water in a penalty area or in temporary water:

• The stroke does not count, and
• The player must correct the mistake under the Rules by playing the right ball from its original spot or by taking relief under the Rules.

Penalty for Playing Wrong Ball in Breach of Rule 6.3c(1): General Penalty.

In match play, the player gets the general penalty (loss of hole):

• If the player and opponent play each other's ball during the play of a hole, the first to make a stroke at a wrong ball gets the general penalty (loss of hole).
• But if it is not known which wrong ball was played first, there is no penalty and the hole must be played out with the balls exchanged.

In stroke play, the player gets the general penalty (two penalty strokes) and must correct the mistake by continuing play with the original ball by playing it as it lies or taking relief under the Rules:

• The stroke made with the wrong ball and any more strokes before the mistake is corrected (including strokes made and any penalty strokes solely from playing that ball) do not count.
• If the player does not correct the mistake before making a stroke to begin another hole or, for the final hole of the round, before returning their scorecard, the player is disqualified.

(2) What to Do When Player's Ball Was Played by Another Player as Wrong Ball. If it is known or virtually certain that the player's ball was played by another player as a wrong ball, the player must replace the original ball or another ball on the original spot (which if not known must be estimated) (See Rule 14.2).

This applies whether or not the original ball has been found.

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