a) Procedure
If a ball may be lost outside a water hazard or may be out of bounds, the player may play another ball provisionally to save time in accordance with Rule 27-1. The player must inform his opponent in stroke play or his counter or a competitor in counting play that he intends to play a provisional ball and must play it before he or his partner goes forward to look for the original ball.
If he fails to do so and plays another ball, that ball is not a provisional ball and becomes a ball in play under penalty stroke and loss of distance (Rule 27-1), whereas the original ball is lost. (Sequence of play from the tee - see Rule 10-3.)
Note: If a provisional ball played in accordance with Rule 27-2a is lost or out of bounds outside a water hazard, the player may play another provisional ball. If another provisional ball is played, it bears the same relationship to the previous provisional ball as the first provisional ball bears to the original ball.
b) Provisional ball becomes ball in play
The player may play a provisional ball until he reaches the place where the original ball is presumed to be. If he plays a shot with the provisional ball from the place where the original ball is presumed to be or from a point closer to the hole than this place, the original ball is lost and the provisional ball becomes the ball in play under penalty stroke and loss of distance (Rule 27-1).
If the original ball is lost outside a water hazard or is out of bounds, the provisional ball becomes a ball in play under penalty stroke and loss of distance (Rule 27-1).
If it is known or virtually certain that the original ball is in a water hazard, the player must proceed in accordance with Rule 26-1.
Exception: If it is known or virtually certain that the original ball is in a hazard (Rule 24-3) or in unusual ground (Rule 25-1c), the player may proceed in accordance with the applicable rule.
Status: 2018