Hi Lynn,This info isn't specifically for your question, but for HCPCS service units.
The Medicare Claims Processing Manual, in chapter 5, outpatient rehab, has section 20 for HCPCS coding requirements. Under section 20.2, there is discussion of timed codes, counting minutes, billing units, etc.
Be aware behavioral codes aren't included in this chapter, but this is the chapter I remembered from my auditing days. Perhaps you could review other chapters in the Claims Processing Manual for discussion of HCPCS service units. However, I would feel comfortable using these section 20.2.C "Units Number of Minutes" as guidelines.
Hope this helps a little.
Have a good weekend,ann