Question: When each of our otolaryngologists takes two weeks of vacation, another physician in town who isn't a member of our practice will fill in for them. Should I code differently when the substitute FP performs a service or procedure? Maine Subscriber Answer: You should submit the applicable E/M service and or procedure code under the regular otolaryngologist's personal identification number (PIN) or group number. Append modifier -Q5 (Service furnished by a substitute physician under a reciprocal billing arrangement) or -Q6 (Service furnished by a locum tenens physician) to the code to indicate that a substitute physician performed the service.