The Official Rules of Golf appear on the About.com Golf site courtesy of the USGA, are used with permission, and may not be reprinted without the permission of the USGA.

A ball on the putting green may be cleaned when lifted under Rule 16-1b. Elsewhere, a ball may be cleaned when lifted except when it has been lifted:

  a. To determine if it is unfit for play (Rule 5-3),
  b. For identification (Rule 12-2), in which case it may be cleaned only to the extent necessary for identification; or
  c. Because it is assisting or interfering with play (Rule 22).

If a player cleans his ball during play of a hole except as provided in this Rule, he incurs a penalty of one stroke and the ball, if lifted, must be replaced.

If a player who is required to replace a ball fails to do so, he incurs the penalty for breach of Rule 20-3a, but there is no additional penalty under Rule 21.

Exception: If a player incurs a penalty for failing to act in accordance with Rule 5-3, 12-2 or 22, there is no additional penalty under Rule 21.

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