Hope this helps:
Psychiatric Testing and Evaluations
In some cases, for various reasons, psychiatric evaluations (90791/90792) and/or psychological
and neuropsychological tests (96101/96146) are completed in multiple sessions that occur on
different days. In these situations, the date of service that should be reported on the claim is the
date of service on which the service (based on CPT code description) concluded.
Documentation should reflect that the service began on one day and concluded on another day
(the date of service reported on the claim). If documentation is requested, medical records for
both days should be submitted.
Psychiatric Testing when provided over multiple days based on the patient being able to
provide information, is billed based on the time involved as described by CPT and the last
date of the test. For more information, see the Medicare Benefit Policy Manual, Chapter
15, Section 80.2, at
https://www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/