The short answer to whether it’s a penalty is this: If both golf balls are on the green before a stroke is played that results in balls colliding, it’s a 2-stroke penalty against the golfer whose stroke caused the collision (the golfer whose ball was at rest when struck is not penalized).
Is there a penalty for hitting another ball on the green?
There is no penalty when a ball played from off the putting green moves another ball. However, in stroke play, when a ball played from the putting green hits another ball on the putting green the person making the stroke incurs a penalty of two strokes.
Can you mark your ball off the green?
You can mark, lift and clean a ball on the green, but it’s a violation to do so when another ball is in motion, as your ball might influence the outcome of that stroke. But it’s OK to clean a ball when you’re taking relief from an immovable obstruction.
What if I hit my ball on a practice swing?
And here’s the ruling: If you accidentally move a ball that is in play with a practice swing, it’s a one-stroke penalty. You must replace the ball to its original position and play it correctly.
What is the penalty for hitting someone else’s golf ball?
Here’s the official definition: “If a competitor makes a stroke or strokes at a wrong ball, he incurs a penalty of two strokes. The competitor must correct his mistake by playing the correct ball or by proceeding under the Rules. Strokes made by a competitor with a wrong ball do not count in his score.