HCPCS Code A0427: ALS1 Emergency Ambulance Transport (2026 Guide)

QUICK ANSWER

A0427 is the HCPCS Level II code for ALS1 emergency ambulance transport, billed when a patient needs at least one advanced life support intervention during an emergency response. It is not a CPT code, even though it is often searched that way, and the ground mileage for the trip is always billed separately with A0425.

● HCPCS, not CPT: A0427 sits inside the ambulance code family, where the level of care (BLS, ALS1, ALS2) and whether the run was an emergency together decide which code applies.

● Modifiers are mandatory: Every ambulance claim needs a two-character origin and destination modifier such as SH or DH, and a missing or wrong pair is the leading reason these claims reject.

● Paid off the Ambulance Fee Schedule: A0427 is reimbursed from Medicare’s Ambulance Fee Schedule, updated by a 2.0% inflation factor for 2026, not the Physician Fee Schedule that governs office codes.

What A0427 Covers

A0427 applies when two things are both true. First, the response is an emergency, meaning an immediate response to a 911 or equivalent call, judged by dispatch protocol and the patient’s condition. Second, the patient requires advanced life support, meaning an ALS assessment or at least one ALS intervention performed by an EMT-intermediate or paramedic that is beyond the scope of a basic EMT. If the run was not an emergency, or only basic life support was needed, A0427 is the wrong code.

Ground mileage for the trip is reported separately with A0425, and the transport code plus the mileage code travel together on the claim. In our experience matching providers with billing partners, the encounters that generate the most confusion are the ones where the clinical picture is obvious but the billing determination is not, because the level of care and the emergency status are coding decisions governed by CMS criteria rather than a loose read of how sick the patient looked.

Is A0427 a CPT or HCPCS Code?

It is a HCPCS Level II code. Ambulance transport is billed under HCPCS, not CPT, which is why searches for an ALS emergency transport CPT code really point to A0427 and its HCPCS rules. The practical consequence is that ambulance claims carry requirements ordinary CPT claims do not, above all the origin and destination modifiers.

That distinction matters because the two code sets are maintained and updated differently. CPT is maintained by the American Medical Association, while HCPCS Level II codes like A0427 are maintained by CMS, and ambulance payment runs on its own separate fee schedule with its own annual update. Treating A0427 like a CPT office code is where a lot of transport billing goes wrong.

The Ambulance Levels of Service

Picking the right transport code is a two-part decision: the level of care (BLS, ALS1, or ALS2) and whether the trip was an emergency. Those two axes produce the core ground ambulance codes, with mileage reported separately.

Two distinctions drive the choice. On level of care, ALS1 (A0427) requires an ALS assessment or at least one ALS intervention, while ALS2 (A0433) is a higher tier that requires three or more separate IV medication administrations, or at least one specified advanced procedure such as manual defibrillation, endotracheal intubation, cardiac pacing, or a central line. On emergency status, the same ALS1 level of care splits into A0427 for an emergency response and A0426 when it is not. Billing ALS2 without the crew documenting those specific interventions is one of the most common ambulance audit targets.

A0427 Fee Schedule and 2026 Updates

A0427 is not paid off the Physician Fee Schedule. It is reimbursed under Medicare’s Ambulance Fee Schedule (AFS), where each level of service carries its own relative value unit, adjusted by a geographic factor and added to a separately calculated mileage payment. Because A0427 is an emergency ALS1 service, it is weighted above basic and non-emergency levels, which is exactly why level-of-service accuracy has a direct dollar impact on the claim.

Two 2026 changes matter. The Ambulance Inflation Factor, the annual update CMS applies to AFS base and mileage rates, is 2.0% for 2026, down from 2.4% in 2025. Separately, the temporary ground ambulance add-on payments, 2% for urban, 3% for rural, and 22.6% for super-rural transports, were extended through December 31, 2027 under the Consolidated Appropriations Act, 2026, after being set to expire on January 31, 2026. CMS also proposed updating the ZIP codes that determine rural and super-rural status using 2020 Census data. In our experience matching providers with billing partners, agencies that fold these add-ons and the geographic designations into their rate checks catch underpayments that others simply post and move past.

Origin and Destination Modifiers

This is the part with no equivalent in standard office billing, and it is the single most common reason ambulance claims reject. Every ambulance claim must carry a two-character modifier that identifies where the patient was picked up and where they were taken. The first character is the origin, the second is the destination, each drawn from a fixed set of location letters:

● D: a diagnostic or therapeutic site other than a hospital or physician office, which includes an urgent care.

● E: a residential, domiciliary, or custodial facility.

● H: a hospital.

● N: a skilled nursing facility.

● P: a physician office.

● R: a residence.

● S: the scene of an accident or acute event.

So an ALS emergency run from a scene to a hospital is reported as A0427-SH, and a run from an urgent care to a hospital is A0427-DH. The most common issue we see providers run into is a clean transport code paired with a missing or transposed modifier, and the claim bounces regardless of how accurate the rest of it is. Knowing how to find the right urgent care medical billing service that treats these modifier pairs as non-negotiable is often what separates a paid claim from a reworked one.

Does an Urgent Care Bill A0427?

No. When a walk-in patient needs emergency transport, the ambulance provider bills A0427 plus mileage, while the urgent care bills its own evaluation and management visit and any stabilizing care it delivered before the patient left. The urgent care never bills the transport itself, even when its own staff arranged the transfer.

Here is where the code actually touches an urgent care. When a walk-in turns out to need ED-level care, for example suspected heart attack, stroke signs, or severe dehydration, E86.0, the clinic stabilizes the patient and arranges emergency transport. The ambulance provider bills A0427 plus mileage (A0425) with origin modifier D for the urgent care and destination H for the hospital. The urgent care bills its own visit and, when the patient is critically ill and stabilized before transfer, potentially critical care, CPT 99291. One question we hear constantly from practice managers is who bills what in that handoff, and knowing the line is what keeps a chaotic transfer from turning into a denied or duplicated claim.

Common A0427 Billing Mistakes

Most practices and transport providers run into the same handful of A0427 errors. Treat them as process fixes rather than one-off slips.

● Using A0427 for a non-emergency transport. That is A0426 for ALS1, or A0428 for BLS.

● Using A0427 when only basic life support was provided. Emergency BLS is A0429.

● Billing ALS2 without the documentation. Report A0433 only when the record shows the specific interventions that meet ALS2 criteria.

● Missing or incorrect origin and destination modifiers. This is the leading cause of ambulance claim rejections.

● Forgetting to report ground mileage with A0425. The mileage code travels with the transport code on the claim.

● Thin patient care report documentation. The report must establish the emergency, the ALS intervention, and medical necessity.

● An urgent care attempting to bill A0427. The transport belongs on the ambulance provider’s claim, not the clinic’s.

Frequently Asked Questions