A ball picked up on the green in accordance with Rule 16-1b may be cleaned. A ball may be cleaned elsewhere if it has been picked up, unless it has been picked up
a) to determine whether it is unfit for play (Rule 5-3);
b) for identification (Rule 12-2), although it may only be cleaned to the extent necessary for identification;
c) to assist or hinder play (Rule 22).
If a player cleans his ball while playing a hole in circumstances other than those provided for in this rule, he incurs a one-stroke penalty and the ball, if picked up, must be returned. If a player fails to put back a golf ball that must be put back, he incurs the basic penalty under the applicable rule, but no additional penalty under rule 21.
Clean ball exception: If a player incurs a penalty because he has not proceeded in accordance with Rule 5-3, 12-2 or 22, no additional penalty is added under Rule 21.
Status: 2018