More than half of all Medicare beneficiaries in Arizona are now enrolled in a Medicare Advantage plan, yet many small practices still treat MA billing the same as traditional Medicare. They are not the same. The rules are different, the timelines are different, and the administrative burden is substantially higher. Understanding those differences is essential for protecting your revenue in 2026.
Two Programs, Two Sets of Rules
Traditional Medicare (Original Medicare, Parts A and B) is administered directly by the federal government through CMS. Claims go to a Medicare Administrative Contractor, payment is based on the national Medicare Physician Fee Schedule, and the rules are uniform across every state. If you are enrolled as a Medicare provider, you can bill for any Medicare beneficiary in any state under the same set of rules.
Medicare Advantage (Part C) is different. Congress authorizes private insurance companies to offer Medicare benefits through contracted plans. Each MA plan sets its own contracted rates, its own prior authorization requirements, its own network rules, and its own timely filing windows. There are currently hundreds of Medicare Advantage plans operating in Arizona, and each one is its own payer relationship.
Accepting Medicare assignment does not automatically make you in-network for any MA plan. You must contract with each plan separately. Being out-of-network for an MA plan can result in claim denials or significantly reduced reimbursement, depending on how the plan is structured.
Timely Filing: A Shorter Window Than You May Expect
Traditional Medicare allows 12 months from the date of service to file a claim. That is one of the more generous timely filing windows in the industry, and many practices have become accustomed to it.
Medicare Advantage plans do not follow this standard. Most MA plans set timely filing limits between 90 and 180 days. Some large plans, including certain Aetna and UnitedHealthcare MA products, use 90-day windows. Miss the deadline, and the denial is almost always final with no appeal pathway.
The practical takeaway for small practices: do not assume your MA claims have the same runway as your traditional Medicare claims. Build a tracking system that flags each claim by payer and deadline, and prioritize MA claims for same-week submission whenever possible.
Prior Authorization: Far More Common in Medicare Advantage
Traditional Medicare has historically required prior authorization only for a narrow set of services. That changed slightly when CMS launched the WISeR Model in January 2026, which introduced prior authorization requirements for 17 specific outpatient procedures in six states, including Arizona. However, these requirements remain limited in scope under traditional Medicare.
Medicare Advantage plans, by contrast, routinely require prior authorization for services that traditional Medicare approves without it. This includes many specialist visits, imaging studies, outpatient procedures, physical and occupational therapy, durable medical equipment, and home health services. Each plan maintains its own list of services requiring authorization, and those lists change on an annual basis.
For small practices in Tucson and Southern Arizona, this means that verifying coverage for a Medicare patient is a two-step process. You first need to confirm whether the patient is on traditional Medicare or an MA plan. If it is an MA plan, you need to know which plan, verify network status, and check authorization requirements before the patient's appointment. Submitting a claim without a required authorization is one of the most common and most preventable denial causes for MA billing.
Payment Rates: Not the Same as the Fee Schedule
Traditional Medicare pays according to the national Physician Fee Schedule published by CMS each year. Every provider receives the same rate for the same service code in the same geographic area, adjusted by locality.
Medicare Advantage plans negotiate their own fee schedules with contracted providers. Those rates may be higher than Medicare, lower than Medicare, or structured as a percentage of the Medicare fee schedule. You will not know what an MA plan pays for a specific service until you review your contract and fee schedule addendum.
In practice, many small practices find that MA reimbursement for certain services is meaningfully lower than what traditional Medicare pays. A 2026 MGMA survey found that 80 percent of medical groups reported Medicare reimbursement below the cost to deliver care, a figure that includes downward pressure from MA plan contracts. Reviewing your MA contracts annually, particularly when plans renew fee schedules at the start of the year, is a revenue protection step that many small practices overlook.
Claims Submission and EOB Differences
Traditional Medicare claims are submitted using the CMS-1500 form (or its electronic equivalent, the 837P) to the regional Medicare Administrative Contractor. MA plan claims go to the private insurer, not to CMS, even though the patient carries a Medicare card.
This distinction trips up practices more often than you might expect. When a patient presents a red, white, and blue Medicare card, front-office staff need to check whether the patient is enrolled in traditional Medicare or an MA plan. An MA member's card will typically display the plan name (Humana, Banner Health Aetna, Blue Cross Blue Shield, etc.) alongside the Medicare identifier. Submitting a claim to the wrong entity wastes weeks and may create timely filing exposure while you wait for a denial and resubmit.
Explanation of Benefits documents also differ. Traditional Medicare EOBs follow a standardized CMS format. MA plan EOBs vary by payer and can be harder to parse for denial reason codes, especially for practices that manage multiple MA contracts.
Network Terminations and Recredentialing
Being in-network with an MA plan requires maintaining active credentialing with that plan. MA plans conduct their own credentialing and recredentialing cycles, separate from traditional Medicare enrollment. A lapsed credentialing application, a missed recredentialing deadline, or a gap in required documentation can result in a network termination that affects every patient you see under that plan.
Arizona has a particularly active MA market, with large plans including Humana, UnitedHealthcare, Aetna, Banner Health Aetna, and Blue Cross Blue Shield all operating in Pima County. Each plan has its own credentialing requirements and recredentialing timelines. Managing those relationships proactively is part of protecting your revenue.
Frequently Asked Questions
Do Medicare Advantage plans pay the same rates as traditional Medicare?
No. Medicare Advantage plans negotiate their own contracted rates, which may be higher or lower than the traditional Medicare fee schedule. Providers must review their specific MA contracts to understand what each plan pays for each service code.
How are timely filing limits different for Medicare Advantage vs. traditional Medicare?
Traditional Medicare requires claims within 12 months of the date of service. Medicare Advantage plans set their own timely filing limits, typically ranging from 90 to 180 days. Practices must track each MA plan's deadline separately to avoid unrecoverable denials.
Do Medicare Advantage plans require prior authorization more often than traditional Medicare?
Yes. MA plans routinely require prior authorization for services that traditional Medicare approves without it, including many outpatient procedures, specialist visits, and imaging studies. Each plan maintains its own authorization list, which changes annually.
Can a provider be in-network for traditional Medicare but out-of-network for a Medicare Advantage plan?
Yes. Accepting Medicare assignment does not automatically make a provider in-network for any Medicare Advantage plan. Each MA plan maintains its own provider network, and providers must contract with each plan separately.
Questions About Your Billing or Revenue Cycle?
A.W. Medical Billing LLC handles clean claim submission, eligibility verification, denial management, credentialing, and revenue cycle management for small and independent practices throughout Tucson and Southern Arizona. We are AAPC-certified, locally owned since 2020, and we offer free consultations.
Call us at (520) 704-5811 or email [email protected].