Answers / Base rate and mileage
Base rate and mileage: how air ambulance disputes are filed
Under the No Surprises Act, one air transport usually produces two billed lines for arbitration, a base rate and a mileage charge. Since the August 2023 TMA III court order, CMS guidance allows both codes of one transport in a single batched dispute, and either code can still be filed alone. In 2025, 9,740 disputes carried both codes, 17,140 only a base code, and 17,207 only a mileage code.
Two codes, one flight
Most transports generate two billed lines. The base rate covers the flight itself and is billed under A0431 for helicopters and A0430 for fixed-wing aircraft. The mileage charge is billed per statute mile under A0436 and A0435. Payers adjudicate the lines separately, and in the 2025 files the two counts track each other closely: 17,478 helicopter base lines against 17,283 helicopter mileage lines. Whether the pair travels to arbitration together or apart is a filing choice, and operators have made both.
What changed in August 2023
The August 2022 technical guidance for IDR entities said the two codes of one air transport could not be considered together in a single dispute. On August 24, 2023, a federal court in Texas vacated that part of the guidance in the case known as TMA III. CMS's November 2023 FAQs then said the base rate and mileage codes of a single transport may be submitted as a batched dispute so long as the batching rules are satisfied, and that nothing prevents either code from being filed alone. The certified IDR entity decides whether a batch is proper. The Departments proposed new batching rules that same month, so confirm the current requirements before filing.
What 2025 filers actually did
Most filers kept the codes apart. Of the 44,087 air ambulance disputes in 2025, 9,740 carried both a base and a mileage code, 17,140 carried a base code alone, and 17,207 a mileage code alone. The files also label 9,813 disputes batched and 34,274 single. The batched group won 90.70 percent at a median of 3.27 times the QPA and took 38 days; single disputes won 92.13 percent at 2.32 times and took 32. Among helicopter transports alone the gap held, at 3.25 times for batched and 2.28 for single.
What the numbers cannot say
The gap between batched and single results describes the files; it does not prove that batching causes it. The files do not show which transports were filed together, how each offer was built, or whether the same operators chose each route. Fixed-wing flights decide higher on their own, at 3.27 times the QPA against 2.36 for helicopters, and they file both ways. Filing separately also means two sets of fees, a $15 administrative fee for each party per dispute plus an IDR entity deposit the winner recovers. Before setting a default, a group should look at how its own base and mileage lines have been decided. Lido IDR sets each offer from the decided results at idrexplorer.com and files each combined or separate dispute for a flat fee per arbitration.
Set the filing rule once
Lido IDR sorts each transport's base and mileage lines, tracks the deadlines on both, and files for a flat fee per arbitration. Talk to an IDR specialist.