Rules of Golf
Rules of Golf Review: When am I allowed to substitute a golf ball on the course?
If you're wondering how often you should be reaching in your bag for a new golf ball (once a round? 10 times a round? once a season?), the answer from this expert might surprise you.
You also might be wondering when the Rules of Golf allow you to exchange a golf ball during a round. The good news is there are a lot of opportunities.
The obvious one, of course, is between holes. If you just made a triple or scuffed one off the cart path, you can banish a golf ball as soon as you hole out. It might suprise you to know that you also can substitute a ball any time you are taking relief (Rule 6.3b). It doesn't matter whether it's free relief or penalty relief. And the ball you substitute doesn't have to be anything like the former (well, so long as it's round and has dimples and you're not playing on a pro tour where the one-ball Local Rule is in effect).
What if you damage a ball and want to replace it during a hole? That's allowed provided the damage is a cut or crack or it's somehow warped. If a mower hacks at it, you're probably safe to replace it. And when that happens, you should substitue another ball by replacing it on the original spot. But keep in mind, you can't take a ball out of play during a hole if it's only scuffed, scraped or the paint is damaged/discolored (unless you're doing so while taking relief).
What do you do if you run out balls? You can beg, borrow or steal from anyone (at your own risk) and play any type of conforming replacement ball including those with the red range stripe on them. Yep, a range ball that's conforming is OK to use.
As you can see, the rules are fairly liberal when it comes to substituting a ball. But remember that there is one time you're not allowed. If you're on the putting green and you mark and lift your ball, you have to put the original ball back down to finish the hole.