What happens if your ball hits another ball on the green?

The situation

You putt from the putting green and your ball rolls into another player's ball that was also on the green. Both balls move.

The rule

Under Rule 11.1a, there is a specific exception for the putting green: if you play a stroke from the putting green and your ball hits another ball at rest on the green, you incur a 2-stroke penalty in stroke play. The other ball must be replaced in its original position. Your ball is played from where it ends up. In match play, there is no penalty — play both balls from where they lie, and the moved ball is replaced. The 2-stroke penalty only applies when both balls are on the green. If either ball was off the green, no penalty applies.

Real example

You're putting from 20 feet on the green. Your partner's ball is on your line six feet from the hole — they forgot to mark it. You putt, hit their ball, your ball goes in. In stroke play: your ball counts, but you add 2 penalty strokes. Their ball is placed back where it was.

What to do on the course

• Always ask other players to mark their ball if it's anywhere near your putting line
• If both balls were on the green: add 2 strokes, play your ball from where it ended up
• The other ball goes back to its original position regardless
• In match play, no penalty — carry on, replace the moved ball

Penalty

2-stroke penalty in stroke play. No penalty in match play.