The codes you will see most
| Code | What it is | Notes |
|---|---|---|
| 90791 | Diagnostic evaluation (intake) | Untimed. Usually once per patient per provider. |
| 90832 | Psychotherapy, 16–37 min | |
| 90834 | Psychotherapy, 38–52 min | The most common therapy code. |
| 90837 | Psychotherapy, 53+ min | Some payers review it more closely. |
| 90846 / 90847 | Family therapy without / with patient | |
| 90853 | Group therapy | |
| 99213–99215 + 90833/90836 | Prescriber visit (E/M) plus psychotherapy add-on | PMHNPs and psychiatrists. |
| 90785 | Interactive complexity | Add-on only, never billed alone. |
Telehealth: place of service 10 (patient at home) or 02 (patient elsewhere), and modifier 95 when the payer requires it. Always check the payer’s current policy.
What makes a claim clean
- Patient name, date of birth and member ID match the card exactly
- Rendering and billing provider NPIs are correct and credentialed with the payer
- CPT matches the session length in the note
- A valid diagnosis code (ICD-10 F-codes for most mental health)
- Correct place of service and modifiers
- Sent within the payer’s timely filing limit
Reading a denial
Each adjustment has a group code, a reason code (CARC) and often a remark code (RARC).
- CO (contractual obligation): the practice can’t bill the patient for it.
- PR (patient responsibility): the patient owes it.
- OA (other adjustment).
Common ones in mental health:
| Code | Meaning | Usual fix |
|---|---|---|
| CO-16 | Missing or invalid information | Read the RARC, correct, resubmit. |
| CO-27 | Coverage terminated | Re-verify, find new coverage, or bill the patient per policy. |
| CO-29 | Timely filing expired | Appeal only with proof of original timely submission. |
| CO-197 | Authorization missing | Request a retro auth if the payer allows. |
| CO-50 | Not medically necessary | Clinical appeal with the note; escalate to the clinician. |
| CO-109 | Wrong payer | Bill the carve-out or correct payer. |
Follow-up
A denial you fixed isn’t done until it pays. The next module, “Payment posting & A/R management”, covers how to work unpaid and denied claims every week until they’re resolved.
The rule you will hear us repeat
Fix the cause, not only the claim. If ten claims denied for the same reason, the eleventh will too unless the setting that caused it is fixed.