99291 and 99292 with Modifier 25

Does the modifier 25 (when other services performed) go on the 99291 or the 99292?
Example:
99291
99292
36556

Any help would be greatly appreciated!
Thanks!

re: 99291 and 99292 with Modifier 25

Add on codes never require a modifier.

Use modifier 25 on 99291 if the service has a 0 or 10 day global period, modifier 57 if a 90 day global period.