Locum tenens is simply when one physician substitutes temporarily for another in the same capacity. There are some differences in billing for services performed by a locum tenens professional, however the 60-day time frame will apply. First and foremost, be sure you are appending modifiers Q5 (Service furnished by a substitute physician under a reciprocal billing arrangement) and Q6 (Service furnished by a locum tenens physician) as appropriate to use. The 60-day rule causes a lot of confusion. Basically, the clock starts ticking from the beginning of service and then runs for 60 consecutive days. It doesn’t matter whether the locum tenens or reciprocal billing physician provides services every day …