Medicare
Federal health insurance program for people 65+, certain younger people with disabilities, and people with End-Stage Renal Disease (ESRD). Administered by CMS through Medicare Administrative Contractors (MACs).
Important: Payer policies change frequently. Always verify current requirements using official payer manuals, provider portals, and direct contact with the payer. DenialPro provides educational guidance and references but does not replace official payer policy. The information on this page is for educational purposes only and may not reflect the most current payer requirements.
Overview
Medicare is the federal health insurance program administered by the Centers for Medicare & Medicaid Services (CMS). It consists of Part A (hospital insurance), Part B (medical insurance), Part C (Medicare Advantage plans offered by private insurers), and Part D (prescription drug coverage). Claims are processed by Medicare Administrative Contractors (MACs) assigned by jurisdiction. Medicare fee-for-service claims follow the National Correct Coding Initiative (NCCI) edits, Local Coverage Determinations (LCDs), and National Coverage Determinations (NCDs).
Official Resources
Timely Filing Limits
Original Medicare claims generally must be filed no later than 1 calendar year after the date of service, subject to CMS exceptions. Do not assume a correction, reopening, or appeal uses the same deadline as an initial claim. Medicare Advantage plans follow the plan and contract rules, which may differ from Original Medicare.
Appeal Time Limits
5 levels of appeal available. Level 1 (Redetermination): 120 days from receipt of remittance. Level 2 (Reconsideration/QIC): 180 days. Level 3 (ALJ): 60 days. Level 4 (DAB): 60 days. Level 5 (Federal Court): 60 days.
Corrected Claim Process
Do not use one universal Medicare correction rule. The correct path depends on claim type, MAC, and the error. Institutional replacement claims may use an appropriate bill type or frequency, while many Part B clerical corrections are handled through reopening or MAC specific correction workflows. Review the assigned MAC instructions and the original claim status before resubmitting.
Prior Authorization
Medicare fee-for-service does not require prior authorization for most services. However, specific services require advance notice or documentation including: Advance Beneficiary Notice (ABN) for non-covered services, and certain DMEPOS, imaging, and power mobility devices may be subject to prior authorization requirements under specific CMS programs.
Referral Requirements
Medicare does not require referrals for specialist visits under Original Medicare (Parts A and B). Medicare Advantage plans may have referral requirements — check the specific plan.
Eligibility Verification
Verify Original Medicare eligibility through the assigned MAC secure provider portal or the HETS 270/271 eligibility transaction. Check Part A and Part B entitlement, Medicare Advantage enrollment, MSP information, hospice and home health indicators when available, and other coverage relevant to the claim.
Claim Status Resources
Check Original Medicare claim status through the assigned MAC secure provider portal, the MAC IVR when appropriate, or a supported HIPAA 276/277 claim status transaction. The 837 is a claim submission transaction and the 835 is a remittance transaction, not the claim status inquiry itself.
Coordination of Benefits
Medicare is typically the primary payer unless the patient has employer-sponsored group health plan coverage based on current employment (for employers with 20+ employees). Use the MSP (Medicare Secondary Payer) questionnaire to determine coordination of benefits.
Modifier Policies
Medicare follows NCCI modifier policies. Key modifiers: 25 (significant, separately identifiable E/M service), 59 (distinct procedural service), GA (ABN on file), GZ (ABN not on file), JW (amount discarded), JZ (no amount discarded). Medicare has specific policies for therapy modifiers (GN, GO, GP) and telehealth modifiers (95).
Telehealth Policies
Medicare expanded telehealth coverage and maintains a List of Telehealth Services on CMS.gov. After the COVID-19 public health emergency, some flexibilities were modified. Use modifier 95 (synchronous telemedicine) or GQ (asynchronous) as applicable. Check current CMS telehealth guidance for the latest covered services and originating site requirements.
Medical Necessity Resources
Medical necessity is governed by LCDs (Local Coverage Determinations) issued by MACs and NCDs (National Coverage Determinations) issued by CMS. Check the CMS MCD (Medicare Coverage Database) for current policies. Documentation must support the diagnosis and treatment provided.
NDC Billing Requirements
NDCs are required for physician-administered drugs billed under the physician fee schedule. Report NDCs using the 5-4-2 format on the CMS-1500 claim form (or equivalent 837 transaction). See CMS MLN Matters articles for formatting requirements.
Common Denial Reasons
- CO-50 (non-covered services/not medically necessary)
- CO-97 (bundling/NCCI edits)
- CO-16 (missing/incomplete information)
- CO-45 (charges exceed fee schedule)
- CO-151 (frequency/number of services not supported)
- CO-109 (claim not covered by this payer — possible MSP issue)
- CO-197 (authorization/notification absent).
Common Rejection Reasons
- Missing NPI
- invalid diagnosis codes
- missing referring provider
- beneficiary identification errors
- deleted CPT codes
- missing/invalid NDC for drugs.
Documentation Requirements
Progress notes must support the level of service billed, medical necessity, and the time and complexity of the visit. For procedures, documentation must support the procedure performed, including operative reports where applicable. See CMS Evaluation and Management documentation guidelines.
Electronic Claim Submission
Submit electronic Original Medicare claims to the assigned MAC using the appropriate 837P or 837I workflow. Institutional providers may have DDE functions through their MAC. Paper claim options and exceptions depend on claim type and CMS rules. Use the assigned MAC instructions rather than assuming every portal supports the same submission method.
Provider Portal
Original Medicare provider work is MAC specific. Use the assigned contractor portal: Noridian Medicare Portal, NGSConnex, myCGS, Palmetto GBA eServices, Novitasphere, First Coast SPOT, or the WPS GHA portal as applicable. Medicare.gov is a beneficiary site and should not be presented as the provider claims portal.
Provider Manual
The CMS Internet-Only Manuals (IOMs) provide official Medicare program instructions. Key manuals: Pub. 100-04 (Claims Processing), Pub. 100-02 (Benefit Policy), Pub. 100-01 (General Information). Also see the National Provider Identifier guide and CMS MLN Matters articles.
Contact Information
Contact your specific MAC for provider inquiries. Contact information is available on the CMS MAC directory page. For beneficiary inquiries, 1-800-MEDICARE (1-800-633-4227).
Educational Notes
Medicare is the most regulated payer — always check LCDs and NCDs before submitting claims. The CMS website offers extensive provider education through MLN (Medicare Learning Network) publications, webinars, and the MLN Matters newsletter. Subscribe to MAC listservs for policy updates.
Always Verify
Payer policies change frequently. This profile is for educational purposes only. Always verify current requirements using the official payer portal, provider manual, and direct communication with the payer.
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