Outpatient Observation Services

Hospital-Based Ambulance Basic Billing Guidelines

For hospital-based ambulance billing under Medicare, services should be billed on the UB-04 form using the ambulance service-specific NPI, not the acute hospital NPI, and claims for inpatient ambulance services are not allowed; instead, separate outpatient claims are required. Follow the below basic billing guidelines to assist in claim submissions.

Type of Bill

  • 13X – Hospital outpatient
  • 85X – CAH

Condition Codes

  • 20 – Demand denial - Billing for denial notice (if applicable)
  • 21 – Insurance denial to allow services to be billed to other insurance 
  • AK – Air Ambulance Required due to medical necessity
  • AL – Specialized Treatment/Bed Unavailable (transported to alternate facility)
  • AM – Non-Emergency Medically Necessary Stretcher Transport Required
  • B2 – CAH Ambulance Attestation (Attestation by CAH that it meets the criteria for exemption from the ambulance fee schedule)

Value Codes

  • 32 – Multiple Patient Ambulance Transport
    • Report this code and the total number of patients transported (in amount field) if more than one patient is transported in a single ambulance trip.
  • A0 – Special ZIP Code Reporting
    • This code is used to report the ZIP code of the location from which the beneficiary is initially placed on board the ambulance.

Revenue Codes

  • 0540
  • Noncovered: 0541, 0542, 0544, 0547, 0549

Ambulance Service HCPCS Codes

  • A0426 – Ambulance service for advanced life support (ALS), non-emergency transport, Level 1 (ALS1)
  • A0427 – Ambulance service, ALS, emergency transport, Level 1 (ALS1-Emergency)
  • A0428 – Ambulance service, basic life support (BLS), non-emergency transport (BLS)
  • A0429 – Ambulance service, basic life support (BLS), emergency ambulance transport service (BLS-Emergency)
  • A0430 – Ambulance service, conventional air services, transport, one-way, fixed wing (FW)
  • A0431 – Ambulance service, conventional air services, transport, one-way, rotary wing (RW)
  • A0432 – Paramedic ALS Intercept (PI), rural area ambulance transport furnished by a volunteer ambulance company
  • A0433 – Ambulance service, ALS, level 2 (ALS2)
  • A0434 – Ambulance service, specialty care transport (SCT)
  • Ambulance Mileage HCPCS Codes
  • A0425 – BLS/ALS mileage, per statue mile
  • A0435 – Air mileage; FW, per statute mile
  • A0436 – Air mileage; RW, per statute mile
  • A0888 – Mileage beyond the closest appropriate facility, non-covered

HCPCS Codes Not Covered by Medicare:

  • A0021 – A0424, A0888 and A0998

Modifiers

Origin & Destination Codes:

  • D – Diagnostic or therapeutic site other than P or H when these are used as origin codes
  • E – Residential, domiciliary, custodial facility
  • G – Hospital based ESRD facility
  • H – Hospital
  • I – Site of transfer (e.g. airport or helicopter pad) between modes of ambulance transport
  • J – Freestanding ESRD facility
  • N – Skilled nursing facility
  • P – Physician's office
  • R – Residence
  • S – Scene of accident or acute event
  • X – Intermediate stop at physician's office on way to hospital (destination code only)

Modifier for Under Arrangement or Direct

Institutional-based providers must report one of the following modifiers with every HCPCS code to describe whether the service was provided under arrangement or directly:

  • QM – Ambulance service provided under arrangement by a provider of services 

or

  • QN – Ambulance service furnished directly by a provider of service

Modifiers used when billing non-covered services:

  • GA – ABN on file (Rarely used - only used in non-emergency situation)
  • GY – Service statutorily excluded or does not meet definition of Medicare benefit
  • QL – Patient pronounced dead after ambulance called

Line-Item Date of Service

MM/DD/YY

Units of Service

Report 1 unit with HCPCs codes A0426, A0427, A0428, A0429, A0430, A0431, A0432, A0433 or A0434

Report number loaded miles with HCPCs codes A0425, A0435 or A0436. Mileage must be reported as fractional units

  • Miles totaling less than 100 miles: Report mileage units rounded up to nearest tenth of a mile. Submit fractional mileage using a decimal in appropriate place (e.g., 99.9). Mileage units reported as 99.99 will become 99.9
  • Miles totaling 100 miles or greater: Report mileage rounded up to nearest whole number mile. Note: Contractors will truncate mileage units totaling 100 and greater that are reported with fractional mileage (e.g., 100.99 will become 100 after truncating the decimal places)
  • Mileage totaling less than 1 mile, include a "0" prior to decimal point (e.g., 0.9)

Total Charges

For line items reflecting HCPCS codes A0426, A0427, A0428, A0429, A0430, A0431, A0432, A0433 or A0434, providers report the actual charge for the ambulance service including all supplies used for the ambulance trip but excluding the charge for mileage.

For line items reflecting HCPCS codes A0425, A0435 or A0436, providers are to report the actual charge for mileage.

When there is no cost incurred for mileage, enter $1.00.

Noncovered Charges

Enter amount of noncovered services, if applicable

Diagnosis Codes

Not required; Condition of the patient can be reported with ICD-10-CM code(s)

NPI CR 7557

Effective for services furnished on or after 4/1/2012:

  • Only non-emergency trips (HCPCS A0426, A0428) require an NPI in the Attending Physician field.
  • Emergency trips do not require an NPI in the Attending Physician field (A0427, A0429, A0430, A0431, A0432, A0433, A0434)

Payment

Fee schedule. Add-on in rural areas and Super Rural Bonus when applicable. Exception to fee schedule: CAH ambulance claims reporting condition code B2 to attest that there is no other provider or supplier of ambulance services that is located within a 35-mile drive of the CAH. Eligible CAHs will be paid 101% of reasonable cost.

Ambulance-Specific Manuals

Posted 3/26/2025