Ambulance Billing Codes Guide

Every ground ambulance claim carries at least two service lines: one for the level of service, which Medicare pays as a base rate, and one for loaded mileage. Each line uses a HCPCS code, and the claim carries modifiers that describe where the patient was picked up and dropped off. Payers compare all of it against the run report, so codes are only as reliable as the documentation behind them.

Ground ambulance base rate codes

• A0428: BLS, non-emergency
• A0429: BLS, emergency
• A0426: ALS1, non-emergency
• A0427: ALS1, emergency
• A0433: ALS2
• A0434: Specialty care transport (SCT)
• A0432: Paramedic intercept, used only in limited rural circumstances that meet specific Medicare conditions

Basic life support (BLS)

BLS applies when the transport required only basic care and monitoring, with no ALS assessment or intervention. The crew must still document why the patient could not safely travel by any other means.

Advanced life support, level 1 (ALS1)

ALS1 requires at least one ALS intervention, meaning a procedure beyond the scope of an EMT-Basic under state rules. On an emergency response, an ALS assessment performed by ALS personnel can also support ALS1 when the dispatch information indicated the patient needed an ALS-level response.

Advanced life support, level 2 (ALS2)

ALS2 requires either:

• At least three separate administrations of one or more medications by intravenous push, bolus, or continuous infusion, not counting crystalloid, hypotonic, isotonic, or hypertonic solutions; or
• At least one of these procedures: manual defibrillation or cardioversion, endotracheal intubation, central venous line placement, cardiac pacing, chest decompression, surgical airway, or intraosseous line.

Specialty care transport (SCT)

SCT applies to an interfacility transport of a critically ill or injured patient who needs ongoing care beyond the scope of a paramedic, provided by one or more health professionals in an appropriate specialty area such as nursing, emergency medicine, respiratory care, or cardiovascular care. A routine hospital-to-hospital transfer with a paramedic crew does not qualify.

Emergency versus non-emergency

Medicare treats a response as an emergency when the ambulance responds immediately to a 911 call or its equivalent. Scheduled and unscheduled non-emergency transports use the non-emergency codes and carry extra documentation requirements, including a Physician Certification Statement for many trips.

Mileage codes

• A0425: Ground mileage, per statute mile, for loaded miles only. Medicare requires mileage under 100 miles to be reported to the nearest tenth of a mile. For pickups in rural areas, Medicare pays an increased rate for the first 17 loaded miles.
• A0888: Non-covered ambulance mileage, used for miles that are not payable, such as miles beyond the nearest appropriate facility.
• A0435 and A0436: Fixed-wing and rotary-wing air mileage.

Air ambulance base codes

A0430 is fixed-wing air transport and A0431 is rotary-wing air transport. Air ambulance claims have their own medical necessity standards, including why ground transport was not appropriate.

Origin and destination modifiers

The two-letter modifier shows the pickup location first and the drop-off location second:

• R residence; H hospital; N skilled nursing facility
• E residential, domiciliary, or custodial facility other than a skilled nursing facility
• S scene of an accident or acute event; P physician’s office
• D diagnostic or therapeutic site other than P or H
• G hospital-based dialysis facility; J freestanding dialysis facility
• I site of transfer between modes of ambulance transport, such as a helipad
• X intermediate stop at a physician’s office on the way to a hospital (destination only)

RH is residence to hospital, SH is scene to hospital, and HN is hospital to skilled nursing facility.

Other modifiers you will see

• QM and QN: used by hospital-based providers to show whether the ambulance service was provided under arrangement (QM) or directly (QN).
• GM: multiple patients on one ambulance trip.
• GA: a required Advance Beneficiary Notice (ABN) was issued. GZ: the item is expected to be denied and no ABN was issued. GY: the service is statutorily excluded or does not meet the definition of a Medicare benefit.

Other ambulance codes

A0998 describes ambulance response and treatment with no transport. Medicare’s ambulance benefit generally requires a transport, so Medicare does not usually pay it, but some Medicaid programs and commercial payers do. A0999 is the unlisted ambulance service code.

Three coding examples

• 911 call, one IV medication given, home to emergency department: A0427 with modifier RH, plus A0425 loaded mileage.
• Cardiac arrest at a workplace, three IV doses of epinephrine, taken to the hospital: A0433 with modifier SH, supported by documented times for each dose.
• Ventilated patient moved between hospitals with a critical care nurse managing infusions: A0434 with modifier HH, only if the documentation shows care beyond the paramedic scope.

Common coding mistakes

• Choosing ALS from the crew’s certification level instead of the documented care
• Counting IV fluids toward the three-medication ALS2 threshold
• Coding every interfacility transfer as SCT
• Using the wrong origin letter for facility pickups
• Billing unloaded miles, or mileage that does not match the route

For more detail, see our articles on ALS and BLS modifier combinations and the seven most common ambulance billing denials, our Medicare ambulance billing guide, and our ambulance coding services.