Match Play
After both players have started play of the hole, the ball farther from the hole is played first. If the balls are equidistant from the hole or their positions relative to the hole are not determinable, the ball to be played first should be decided by lot.
Exception: Rule 30-3c (best-ball and four-ball match play).
Note: When the original ball is not to be played as it lies and the player is required to play a ball as nearly as possible at the spot from which the original ball was last played (see Rule 20-5), the order of play is determined by the spot from which the previous stroke was made. When a ball may be played from a spot other than where the previous stroke was made, the order of play is determined by the position where the original ball came to rest.
c. Playing Out of Turn
If a player plays when his opponent should have played, there is no penalty, but the opponent may immediately require the player to cancel the stroke so made and, in correct order, play a ball as nearly as possible at the spot from which the original ball was last played (see Rule 20-5).

Stroke Play
During Play of Hole
After the competitors have started play of the hole, the ball farthest from the hole is played first. If two or more balls are equidistant from the hole or their positions relative to the hole are not determinable, the ball to be played first should be decided by lot.
Exception: Rules 22 (ball assisting or interfering with play) and 31-5 (four-ball stroke play).
Note: When the original ball is not to be played as it lies and the player is required to play a ball as nearly as possible at the spot from which the original ball was last played (see Rule 20-5), the order of play is determined by the spot from which the previous stroke was made. When a ball may be played from a spot other than where the previous stroke was made, the order of play is determined by the position where the original ball came to rest.
c. Playing Out of Turn
If a competitor plays out of turn, there is no penalty and the ball is played as it lies. If, however, the Committee determines that competitors have agreed to play out of turn to give one of them an advantage, they are disqualified.