It is all too easy to play a wrong ball and if you do, it is a loss of hole penalty in match play or two stroke penalty in stroke play. Make sure you can identify your ball by putting your own distinctive mark on it – do not depend on remembering the brand and number on the ball. It is good etiquette to tell your fellow competitors or opponent what ball you are playing, in particular when playing a provisional ball. To correctly identify a ball that may be partially hidden or embedded, first mark its position, lift it, identify it and replace it in the exact spot and allow your marker or opponent to observe the lifting process. You may not touch/rotate your ball in play to identify it without marking it and the penalty for not correctly following the procedure outlined is one stroke, Rule 12-2. If you do play a wrong ball in stroke play you must correct the error before you tee off from the next teeing ground otherwise you are disqualified. Go back and find your own ball and add a two stroke penalty to your score for the hole. If your original ball is lost then you will also have a stroke and distance penalty. Strokes played with a wrong ball are not counted in your score for the hole. It can be very penalising in stroke play to play a wrong ball so avoid a potentially card-ruining breach by putting an identifying mark on your ball.