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CMS Rules & Reference

Quick-reference definitions and direct links to official CMS sources — eligibility, billing, medical necessity, rural designations, and more.

Key Definitions & Concepts

Plain-English summaries with links to official CMS sources.

CMS Resources Library

Direct links to CMS manuals, fee schedules, and regulatory guidance.

Fee Schedule

CY 2026 Ambulance Fee Schedule

Official CMS page for the Ambulance Fee Schedule, including payment rates, ZIP code files, and locality files.

Ambulance Fee Schedule ZIP Code Files

Downloadable ZIP code to carrier locality crosswalk files used to determine urban/rural designation.

Ambulance Inflation Factor (AIF) History

Historical AIF adjustments applied to the ambulance fee schedule conversion factor each calendar year.

Coverage & Eligibility

Medicare Benefit Policy Manual – Chapter 10 (Ambulance)

Definitive CMS manual chapter covering ambulance coverage criteria, medical necessity, and conditions of payment.

Medicare Ambulance Suppliers – Enrollment & Conditions

CMS enrollment requirements and conditions of participation for ambulance providers.

Billing & Coding

CMS Ambulance Services MLN Fact Sheet

MLN educational resource covering billing requirements, modifiers, levels of service, and documentation.

Medicare Claims Processing Manual – Chapter 15 (Ambulance)

Detailed billing and claims processing instructions for ambulance providers, including modifier usage.

CMS HCPCS Code Lookup

Official source for HCPCS Level II code sets including ambulance codes A0425–A0436.

OIG Work Plan – Ambulance Services

OIG oversight priorities for ambulance billing compliance — useful for internal audit planning.

Prior Authorization

Ambulance Prior Authorization Program

CMS prior authorization requirements for repetitive non-emergency ambulance transport.

Prior Authorization for Repetitive, Scheduled Non-Emergency Ambulance Transport

Fact sheet on the national expansion of ambulance prior authorization requirements.

NEMT

NEMT – Medicaid Non-Emergency Medical Transportation

Medicaid.gov overview of NEMT benefits, state plan requirements, and managed care.

CMS NEMT Informational Bulletin

CMS guidance on NEMT as a required Medicaid benefit and broker model considerations.

Final Rules

CY 2026 Physician Fee Schedule Final Rule (Ambulance Provisions)

Federal Register final rule containing 2026 ambulance fee schedule payment policy changes.

Forms & Tools

CMS ICD-10 & Diagnosis Coding for Ambulance

ICD-10-CM resources relevant to documenting medical necessity on ambulance claims.