CPT Code 99356: Prolonged inpatient service, first hour

When to Use CPT 99356

Use CPT code 99356 when billing for prolonged inpatient service, first hour. This code is used by licensed therapists (LCSW, LPC, MFT, Psychologist) for outpatient sessions.

Adding CPT 99356 to a Superbill

When generating a superbill with CPT 99356, include the ICD-10 diagnosis code, date of service, fee charged, amount paid, and your NPI number. Superbilled pre-fills common therapy CPT codes automatically.

Common ICD-10 Pairings

These diagnosis codes are frequently used alongside CPT 99356:

Documentation Requirements

Document the additional inpatient time beyond the typical E/M service. Include clinical justification for the extended bedside or unit time.

Common Denial Reasons

• ✗ Billed without a qualifying inpatient E/M service
• ✗ Prolonged time threshold not met
• ✗ Missing clinical justification for extended inpatient encounter

Got one of these on a remittance? Decode the denial code.

Reimbursement Expectations

OON reimbursement typically 45-65% of UCR. Expect $45-$130 for the first prolonged hour.