Ambulance and EMS Transport Medical Coding: Cheat Sheet and Tips

Posted by: Edelberg & Associates

Emergency situations call for unique medical coding of non-physician provider services
Ambulance codes and guidelines are uniquely applicable to non-physician providers. To make coding these services even more of a challenge, procedure codes relevant to emergency medical service (EMS) providers aren’t found in the CPT® codebook. Instead, coding guidelines for ambulance and EMS transport codes come primarily from Medicare transmittals and MedLearn updates.

Payers generally cover ambulance services, including fixed and rotary wing services, for patients whose medical condition is such that air transport is medically necessary. To assure transport is medically necessary, you must consider both the patient’s condition and the method of transportation. This can be a challenging process, which depends on the documentation paramedics and emergency medical technicians (EMTs) provide in the field.

Differentiate Emergency vs. Non-emergency Response

To prevent coding errors, use extreme care when differentiating emergency from non-emergency transports. This often requires additional education for ambulance providers to assure their documentation of a patient’s conditions accurately describes when an emergency condition existed, or when an emergency transport was required.

CMS defines an emergency response as, corresponding immediately at the BLS or ALS1 level of service to a 911 call or the equivalent.  An immediate response is defined as a response by the ambulance supplier that begins as quickly as possible to the call. Emergency response is based on internal protocols, which consider the information received during the call. The call does not have to come through a 911 system.

All scheduled transports are considered non-emergency, and include routine transports to nursing homes, patient homes, and end-stage renal disease (ESRD) facilities.

Break Down Ambulance Services Categories

In the Ground Ambulance Services section of the ambulance fee schedule, there are seven categories of ground ambulance services (ground refers to both land and water transportation) and two categories of air ambulance services. The level of service is based on the patient’s condition, not the vehicle used. This is a challenge for many coders.

In addition to the HCPCS Level II procedure codes and standard set of modifiers (see Chart A), a unique set of modifiers (see Chart B) are required to identify the origin and destination, which are affixed to the procedure code. Mileage must also be calculated, which presents additional challenges if this information is not clearly documented (ambulance coders are all too familiar with programs that estimate mileage between pick-up and drop-off points to assure accuracy for mileage calculations).

Chart A: Common modifiers for ambulance services


Use when billing for statutorily-excluded services. For example, patient transport is for a non-covered condition that does not meet the definition of any Medicare benefit. The provider is expecting a denial.Refer to the payer’s modifier fact sheet for additional information on modifier GY.


Use when the patient is pronounced deceased after the ambulance is called. The patient is pronounced dead after the ambulance is called, but before transport. Ground providers can bill a BLS service along with modifier QL.See CMS Internet-Only Manual, 100-2, Medicare Benefits Policy Manual, chapter 10, section 10.2.6.

Air providers can use the appropriate air base rate code (fixed wing or rotary wing) with modifier QL. There will be no rural allowance or mileage billed. View the article for air ambulance suppliers. See CMS Internet-Only Manual, 100-2, Medicare Benefits Policy Manual, chapter 10, section 10.4.9. GM

Use when more than one patient is transported in an ambulance and there are documented details of the transport. Used by both ground and air transports. See CMS Internet-Only Manual, 100-4, Medicare Claims Processing Manual, chapter 15, section 30.1.2. GA

The provider or supplier has provided an Advance Beneficiary Notice (ABN) to the patient. GZ

The provider or supplier expects a medical necessity denial, but did not provide an ABN to the patient.There are only four situations where the Limitation of Liability provision applies to ambulance suppliers. A CMS-approved ABN form is needed by an ambulance company to reverse the limitation of liability in those situations.

Chart B: Specialty modifiers for reporting ambulance services (including origin and destination codes and their descriptions)




Diagnostic or therapeutic site other than P or H when these are used as origin codes


Residential, domiciliary, custodial facility (other than 1819 facility)


Hospital based ESRD facility




Site of transfer (e.g., airport or helicopter pad) between modes of ambulance transport


Freestanding ESRD facility


Skilled nursing facility


Physician’s office




Scene of accident or acute event


Intermediate stop at physician’s office on way to hospital (destination code only)

Ground Ambulance Services

A0425 Ground mileage, per statute mile requires documentation and/or calculation of mileage between sites.

A0426 Ambulance service, advanced life support, nonemergency transport, level 1 (ALS1) includes transportation by ground ambulance and medically necessary supplies and services. The response personnel are required to document an ALS assessment, or to provide at least one ALS intervention.

Advanced life support assessment is defined as:
1. Assessment performed by an ALS crew as part of an emergency response that was necessary; or
2. The patient’s reported condition at the time of dispatch was such that only an ALS crew was qualified to perform the assessment.  An ALS intervention includes procedures that are beyond the scope of an EMT-basic. Personnel qualified for ALS are trained EMT-intermediates or paramedics.

Often, the ALS assessment does not indicate that the patient required a level of service consistent with ALS, but that is only determined after the assessment is performed. Documentation is critically important to identify signs and symptoms that required the assessment and the results of the assessment, including the condition of the patient prior to and during transport.

  • A0427 Ambulance service, advanced life support, emergency transport, level 1 (ALS1 – emergency): The provision of ALS1 services as an emergency response applies. For ALS1, ALS2, and specialty care transport (SCT), the emergency condition is assumed, but documentation is critical to support these services.
  • A0428 Ambulance service, basic life support, nonemergency transport (BLS) defines transportation by ground ambulance vehicle, with medically necessary supplies and services, as well as BLS services. The ambulance must be staffed by a qualified EMT-basic consistent with state rules and regulations, which may vary from state to state. Coding for these services requires an understanding of state regulations and the ambulance provider’s assurance that providers meet the criteria for each level of transport. For example, only in some states is an EMT-basic permitted to operate limited equipment on board the vehicle, assist more qualified personnel in performing assessments and interventions, and establish a peripheral intravenous (IV) line.
  • A0429 Ambulance service, basic life support, emergency transport (BLS emergency) describes the provision of BLS services, but for response to an emergency. Emergency response is defined as immediate response to a 911 (or similar) call. A call is determined to be an emergency based on the information available to the dispatcher, who is expected to follow existing protocols. Be familiar with these protocols for ambulance providers to assure coding is consistent with dispatch and emergency criteria.
  • A0433 Advanced life support, level 2 (ALS2) requires three or more different administrations of medications by IV push/bolus or by continuous infusion, excluding crystalloid, hypotonic, isotonic, and hypertonic solutions (dextrose, normal saline, Ringer’s lactate), or medically necessary ground transportation, supplies and services, and the provision of at least one of the following ALS procedures:
  • Manual defibrillation/cardioversion
  • Endotracheal intubation including the monitoring and maintenance of an endotracheal tube that was inserted prior to the transport, which also qualifies as an ALS2 procedure.
  • Central venous line
  • Cardiac pacing
  • Chest decompression
  • Surgical airway
  • Intraosseous line
  • A0434 Specialty care transport (SCT) is an interfacility transportation of a critically injured or ill beneficiary by a ground ambulance, including the provision of medically necessary supplies and services, at a level of service beyond the scope of the EMT paramedic. SCT is required when a beneficiary’s condition requires ongoing care that must be provided by one or more health professionals in an appropriate specialty area (e.g., emergency, critical care nursing, emergency medicine, respiratory care, cardiovascular care, or a paramedic with additional training).

Be cautious when using this code for chronic ventilator-dependent patients whose transport would not qualify for SCT unless their condition is considered acute or the patient has developed emergency signs and symptoms for other conditions.

Air Ambulance Services

The two categories of air ambulance services are fixed wing (airplane) and rotary wing (helicopter). The air ambulance mileage rate is calculated per actual loaded (patient onboard) miles flown, and is expressed in statute miles (not nautical miles).

  • A0430 Ambulance service, conventional air services, transport, one way (fixed wing). Fixed wing air ambulance (FW) is used when the patient’s medical condition requires immediate and rapid transportation that can’t be provided by ground ambulance either because the point of pick-up is inaccessible, the nearest hospital with appropriate facilities is far away, or the road is impassable due to heavy traffic or other obstacles. Mileage is identified with A0435 Fixed wing air mileage, per statute mile.
  • A0431 Ambulance service, conventional air services, transport, one way (rotary wing). Rotary wing air ambulance (RW) service is used when a patient requires rapid transportation due to medical condition, and there are transportation challenges applicable to fixed wing transportation (traffic, distance, etc.). Report mileage using A0436 Rotary wing air mileage, per statute mile.
  • A0888 Noncovered ambulance mileage, per mile (e.g., for miles traveled beyond closest appropriate facility). Report this code when the reason for the ambulance trip is not covered by Medicare, and you do not expect Medicare payment.

Non-covered Services

Effective Jan. 1, 2012, CMS allows ambulance providers to bill procedure codes for non-covered ambulance services. This does not include supplies associated with a covered ambulance transport. Per CMS Internet Only Manual (publication 100-04, chapter 15, section 30.1), those supplies are included in the base rate.
If the supplies are associated with a non-covered service, they are billable to Medicare with modifier GY Item or service statutorily excluded, does not meet the definition of any Medicare benefit or for non-Medicare insurers, is not a contract benefit. Procedure codes A0021-A0424 and A0998 Ambulance response and treatment, no transport are billable procedure codes and must include modifier GY; however, they are not payable by Medicare.
Effective for claims with dates of service on and after Oct. 1, 2013, payment for non-emergency BLS transports of individuals with ESRD to and from renal dialysis treatment facilities will be reduced by 10 percent. The reduced rate will be calculated and applied to HCPCS Level II code A0428 when billed with destination modifier code “G” or “J,” and the associated mileage (code A0425). A claim adjustment reason code of 45 Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement and group code CO Contractual obligation will be on the remittance advice notice.

Make sure your coding and billing staffs are aware of these changes. The 10 percent reduction applies to beneficiaries with ESRD who are receiving a non-emergency BLS transport to and from renal dialysis treatment.

A Medicare beneficiary receiving maintenance dialysis on an outpatient basis does not ordinarily require ambulance transportation for dialysis treatment, whether the facility is independent or part of a hospital. Ambulance services furnished to a maintenance dialysis patient are not payable unless documentation submitted with the claim shows that the patient’s condition requires ambulance services and the facility meets the destination requirements. Medical necessity must be documented for claims for non-routine round trip ambulance services to outpatient dialysis facilities. Medicare has discretion to override or reverse the reduction on appeal, if they deem it appropriate, based on supporting documentation.

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