Question: What is the rule for billing CRNA services as locum tenens? Florida Subscriber Answer: Locum tenens is reserved for physicians, not CRNAs or other anesthesia providers. You can sometimes bill for locum tenens service when a physician joins your group to fill in for another physician for a certain period of time (such as when the physician takes time for maternity leave). When applicable, you include modifier Q6 (Service furnished by a locum tenens physician) on the locum tenens physician's claims.