How do ambulance services bill Medicare?

What are the steps to bill Medicare for an ambulance transport?

An ambulance service bills Medicare by coding each transport as one base-rate line for the level of service plus one mileage line for loaded miles, adding a two-letter origin and destination modifier, and sending the claim to its Medicare Administrative Contractor within 12 months. Medicare pays 80% of the fee schedule amount after the Part B deductible, and the agency must accept assignment. The steps below follow one transport from the call to the payment.

1. Enroll first. Independent ambulance suppliers enroll with CMS on the CMS-855B and bill under their own Medicare number. Hospital-based services bill under the hospital.
2. Capture the run at dispatch. Record the call type (emergency or scheduled), pickup address and ZIP code, destination, and crew certification level.
3. Check eligibility. Confirm Part B coverage and whether a Medicare Advantage plan or a Part A skilled nursing facility stay changes who pays. Eligibility and coverage errors caused 24% of denials in our claim audit across all specialties.
4. Collect medical necessity documentation. The patient care report must show why other transport was unsafe. Non-emergency runs also need a Physician Certification Statement and, for repeat trips, a prior authorization number.
5. Code the level of service. Pick the HCPCS base code from the care given, not the vehicle that showed up.
6. Add modifiers and mileage. Put the origin and destination modifier on both lines and bill loaded miles to one decimal place.
7. Submit the claim. Suppliers send an 837P (paper CMS-1500) with place of service 41 for ground or 42 for air. Hospitals send an 837I (paper UB-04) with revenue code 0540.
8. Post the remittance and work denials. Read the 835 remittance advice, bill the 20% coinsurance to the patient or secondary payer, and appeal wrong denials. In our billing reviews, 19% of denied claims were never reworked or appealed.

If you want the whole cycle run for you, full-service medical billing covers each of these steps inside your existing ePCR and billing system.

Which ambulance billing codes does Medicare use?

Medicare ground ambulance claims use seven HCPCS base codes, one per level of service, plus A0425 for mileage. Each level carries a relative value unit (RVU) that sets its share of the base rate.

Code the level the patient needed and received. An ALS unit that only gave basic care bills BLS. An ALS1 emergency claim needs an ALS assessment or at least one ALS intervention in the record, and ALS2 needs three separate medication administrations by IV push, bolus or infusion, or one listed procedure such as intubation or cardiac pacing. The gap between levels is large: SCT pays 325% of the BLS non-emergency base rate and ALS1 emergency pays 190%.

Our medical coding service reviews level of service against the patient care report before the claim goes out.

How do ambulance modifiers work on a Medicare claim?

Every Medicare ambulance line needs a two-character modifier: the first letter is where the patient was picked up and the second is where they were taken. A home-to-hospital run is RH. A hospital discharge to a skilled nursing facility is HN.

Other ambulance modifiers you will use

• QM and QN: institutional providers only. QM means the transport was furnished under arrangement, QN means the provider furnished it directly.
• GM: more than one patient on the same trip. Put GM on every line and send documentation.
• QL: patient pronounced dead after the ambulance was called. CMS pays the BLS base rate with no mileage, but some contractors edit QL claims differently, so check your MAC.
• GA and GY: GA shows a valid Advance Beneficiary Notice is on file. GY marks a service Medicare excludes by statute.

Modifier mistakes are small per claim and constant in volume. Origin and destination modifier errors appeared on 6% of ambulance claims in our audit, and each one turns into a denial or a request for records.

How is Medicare ambulance mileage billed?

Medicare pays only loaded miles, measured from the pickup point to the destination while the patient is on board. Since January 1, 2011, trips under 100 covered miles are billed to the nearest tenth of a mile, so a 12.37 mile trip bills as 12.4 units. Trips of 100 miles or more are rounded to whole miles, and anything under one mile is written with a leading zero, such as 0.6.

The ZIP code of the pickup point goes on every claim, because it decides whether urban, rural or super-rural rates apply. If the patient goes past the nearest appropriate facility, Medicare pays mileage only to that nearest facility, and the claim narrative should explain why a farther destination was needed.

What documentation do Medicare ambulance billing guidelines require for non-emergency transports?

A non-emergency transport is covered only when the patient is bed-confined or their condition makes other transport unsafe, and the record has to prove it. Bed-confined means all three: unable to get up from bed without help, unable to walk, and unable to sit in a chair or wheelchair.

The Physician Certification Statement

• Repetitive scheduled transports: a PCS dated no earlier than 60 days before the transport.
• Unscheduled or one-time transports for facility residents: a PCS obtained within 48 hours after the transport. If the physician is not available, a PA, NP, CNS, RN, LPN, social worker, case manager or discharge planner may sign.
• No signature after 21 days: the agency may bill if it can show documented attempts, such as a signed Postal Service return receipt.

Prior authorization for repetitive transports

Repetitive scheduled non-emergent transport means three or more round trips in 10 days, or at least one round trip a week for three weeks, which covers most dialysis and wound care runs. Medicare’s prior authorization model for these runs has applied nationwide since August 1, 2022. One approval covers as many as 40 round trips over 60 days and comes with a unique tracking number that goes on each claim. Without it, claims after the third round trip go to prepayment review. Our eligibility and prior authorization team tracks approval windows so trip 41 is not a surprise.

Paperwork is the most common failure. In our audit, Physician Certification Statements were missing or unsigned on 18% of non-emergency transports, against 7.8% of paid claims underpaid against contract across all specialties, 6% of ambulance claims with modifier errors and 4% with wrong Medicaid mileage units.

How does the Medicare ambulance fee schedule calculate payment?

The Medicare ambulance fee schedule pays a base rate plus mileage. The base rate is the level’s RVU times the national conversion factor, with 70% of that amount adjusted by the practice expense GPCI for the pickup location and 30% left unadjusted. Mileage is paid per loaded mile. CMS raised rates 2.0% for 2026 through the ambulance inflation factor, which is CPI-U of 2.7% less a 0.7% productivity adjustment.

Add-ons and penalties

• Temporary add-ons of 2% urban, 3% rural and 22.6% super-rural on the base rate, plus a 50% bump for the first 17 rural miles, run through December 31, 2027 after the Consolidated Appropriations Act, 2026.
• Organizations selected for the Ground Ambulance Data Collection System that did not report can lose 10% of their fee schedule payments for the following year.

Worked example: one ALS1 emergency transport

Take a suburban agency and an ALS1 emergency run of 12.4 loaded miles. CMS publishes the actual 2026 conversion factor and mileage rate in its public use file, so for readable math we use round illustrative figures: a $280 conversion factor, a GPCI of 1.05 and an $8.50 mileage rate, plus the 2% urban add-on.

• Base: $280 x 1.90 = $532.00. GPCI factor: (0.70 x 1.05) + 0.30 = 1.035, so $532.00 x 1.035 = $550.62. Urban add-on: $550.62 x 1.02 = $561.63.
• Mileage: 12.4 x $8.50 = $105.40, plus 2% = $107.51.
• Allowed amount: $561.63 + $107.51 = $669.14. Medicare pays 80%, or $535.31. The patient or secondary payer owes 20%, or $133.83, once the $283 Part B deductible for 2026 is met.

Now code the same run BLS emergency because the chart does not document an ALS intervention: $280 x 1.60 x 1.035 x 1.02 = $472.95. That is $88.68 less per transport. At 150 ALS1 emergency runs a month, weak documentation of ALS care is worth $13,302.00 a month.

The same math prices the PCS problem. An agency running 300 non-emergency BLS transports a month with an 8-mile average trip bills $295.60 base plus $69.36 mileage, or $364.96 per claim. If 18% lack a valid PCS, 54 claims a month, or $19,707.84, sit at risk of denial.

Why does Medicare deny ambulance claims?

Medicare denies ambulance claims mostly because the record does not prove the transport was necessary. CMS found a 10.4% improper payment rate for ambulance services in its 2025 report, about $452.6 million. Insufficient documentation drove 46.7% of those improper payments, medical necessity 24.9%, missing documentation 11.5% and coding and other causes 16.9%.

The mistakes behind those numbers

1. Crew narratives that list vitals but not the reason. Write why a wheelchair van or car was unsafe: fall risk, oxygen, restraints, monitoring.
2. PCS collected at billing instead of at scheduling. By then the signer is gone. King-American Ambulance moved PCS collection to the scheduling desk, as shown in the King-American Ambulance case study, and cut days in AR from 71 to 38.
3. Modifiers set by the biller, not the crew. Set origin and destination at dispatch, where the facts are known.
4. Billing Part B during a covered SNF stay. Most transports during a Part A skilled nursing stay are bundled into the facility’s payment.
5. Missing the filing window. Medicare’s limit is one calendar year from the date of service. Timely filing caused 6% of denials, and only 4% of those were recovered.
6. Resubmitting instead of appealing. Appeals filed by Luxen were overturned 68% of the time, while duplicate resubmissions just deny again. Our denials and AR recovery work starts with the oldest dollars first.

Should an ambulance agency bill Medicare in-house or outsource EMS billing?

Bill in-house if you have a certified coder who reads every patient care report, someone who owns PCS follow-up daily, and reporting that shows denials by reason each month. Outsource when those jobs sit with dispatch or a shift supervisor. Outsourced billing usually costs 3% to 6% of collections. Ambulance agencies carried 37% of AR past 90 days in our billing reviews, so the cost of doing nothing is often higher than the fee. For the full revenue cycle view, including benchmarks and vendor pricing, see our guide to ambulance revenue cycle management, and if you are comparing vendors, start with how to evaluate medical billing companies.

How do Medicare ambulance coverage rules differ for emergency and non-emergency transports?

Emergency transports are judged on the patient’s condition at the time of the call. Non-emergency transports need paperwork before or shortly after the run, and repetitive ones need prior authorization.

Ambulance and EMS agencies

Independent suppliers carry the full rule set: 837P claims, place of service 41, loaded mileage in tenths and a PCS for every non-emergency run. The ambulance-specific audit numbers show where they lose money. Mileage units were wrong on 4% of Medicaid transport claims, and dual-eligible patients mean the Medicaid claim often follows the Medicare one. Build PCS and modifier capture into dispatch rather than billing.

Hospitals with their own ambulance

Hospital-based services bill on the 837I with revenue code 0540 and add QM or QN to show whether the transport was under arrangement or furnished directly. Critical access hospitals with condition code B2 can be paid at 101% of reasonable cost instead of the fee schedule. Discharges to a nursing facility use HN, and interfacility transfers are covered only to the nearest hospital that can give the needed care. See hospital billing for how facility claims differ.

Skilled nursing facilities

During a covered Part A stay, most ambulance trips are bundled into the SNF payment, so an ambulance Part B claim for that resident is denied. The exceptions bill separately: emergency transports, dialysis runs coded with N and G or J, cardiac catheterization, CT, MRI, angiography, radiation therapy and outpatient surgery in an operating room. The SNF, not Medicare, pays for routine trips. Our skilled nursing facility billing page covers consolidated billing in full.

Dialysis and nephrology

Dialysis runs are the textbook repetitive scheduled transport, with modifier pairs such as RJ for home to a freestanding ESRD facility or RG for a hospital-based one. They need prior authorization after the third round trip, one approval covers 40 round trips in 60 days, and a nephrologist’s PCS dated within 60 days. Many patients walk with help, so the record must show why they are bed-confined. See nephrology billing.

Primary care and physician offices

Physician offices do not bill ambulance transports, but their staff sign the certifications that decide whether the claim is paid. A PCS that says only transport needed will not survive review. It should state the condition, such as a hip fracture with inability to bear weight, and why a car or wheelchair van is unsafe. Offices also appear as origin or destination code P, or X for an intermediate stop.

Behavioral health

Psychiatric transports are covered when the patient needs restraint, supervision to prevent harm, or sedation that makes other transport unsafe. A patient who is calm and able to walk safely usually does not qualify. Document restraints, sitter use and behavior at pickup in the narrative, because medical necessity drove 24.9% of improper ambulance payments in CMS’s 2025 data.