Medicare MAC Lookup
Select your state to find which Medicare Administrative Contractor (MAC) processes your claims, plus your DME MAC for durable medical equipment.
What is a MAC?
A Medicare Administrative Contractor (MAC) is a private company that CMS contracts with to process and pay Medicare Part A and Part B claims in a specific geographic region. MACs are the frontline of Medicare claims administration — they handle claim submissions, payments, appeals, provider enrollment, and beneficiary inquiries.
There are currently 12 A/B MACs covering different jurisdictions across the United States, plus 4 DME MACs that handle Durable Medical Equipment claims separately. Your MAC is determined by the state where the service was provided, not where you live.
Why your MAC matters for billing disputes
When you find an error on a Medicare bill or Explanation of Benefits (EOB), your MAC is the first point of contact. Knowing which MAC processes your claims helps you:
- File appeals faster — Each MAC has its own appeals submission process and mailing address
- Get coverage decisions — MACs issue Local Coverage Determinations (LCDs) that define what Medicare covers in your region
- Verify claim status — Check whether a claim was received, processed, or denied
- Report billing issues — Report suspected fraud, duplicate billing, or incorrect charges directly to your MAC
- Understand regional rules — MACs can have different Local Coverage Determinations that affect what is covered in your area
A/B MACs vs. DME MACs
A/B MACs process claims for Medicare Part A (hospital/inpatient) and Part B (physician/outpatient) services. DME MACs handle claims specifically for Durable Medical Equipment, Prosthetics, Orthotics, and Supplies (DMEPOS) — things like wheelchairs, oxygen equipment, CPAP machines, and diabetic supplies.
Your A/B MAC and DME MAC may be different companies. A billing error on a hospital or doctor visit goes to your A/B MAC, while a dispute about medical equipment goes to your DME MAC.
How MACs handle Local Coverage Determinations
Unlike National Coverage Determinations (NCDs) that apply everywhere, Local Coverage Determinations (LCDs) are issued by individual MACs and only apply to their jurisdiction. This means a procedure that Medicare covers in one state might not be covered in another, depending on the MAC's LCD.
If a claim is denied based on an LCD, you have the right to appeal. Knowing your MAC helps you find the specific LCD that applies and understand the coverage criteria.
Check your medical bill for other errors
Use our free tools to verify CPT/HCPCS codes, check for NCCI bundling violations, or generate a dispute letter with regulatory citations.
Look Up a CPT CodeMore free billing tools
BillError provides free tools to help you understand and dispute medical bills:
- CPT/HCPCS Code Lookup — Look up any procedure code for RVU breakdown, Medicare rates, and MUE limits
- NCCI Code Pair Checker — Check if two procedure codes should not be billed together
- Bill Math Checker — Verify the arithmetic on any bill
- Dispute Letter Generator — Create a dispute letter with regulatory citations for any bill type
About this tool
This tool uses CMS MAC jurisdiction data to map each state to its assigned A/B MAC and DME MAC. CMS periodically reassigns jurisdictions when contracts change. MAC contact information is sourced from CMS public data.
Learn more
For a comprehensive guide to understanding and challenging medical bills, read our complete guide to medical billing errors. To learn about your billing rights in your state, see medical bill rights by state.