Medicare prior authorization: how the approval process works

Two things reshaped Medicare prior authorization for 2026: the CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) put hard decision deadlines on Medicare Advantage plans, and the CMS Innovation Center's WISeR Model added mandatory prior authorization for 17 services in Original Medicare across six states. Denials keep landing on billing desks anyway.

This guide is written for billers and authorization coordinators who process Medicare prior authorizations at volume. Every section leads with the operative fact.

Who requires it

Original Medicare (Parts A and B) requires prior authorization for a defined, limited set of services. Medicare Advantage (Part C) plans require it extensively, covering nearly every enrollee for at least some services. Which program covers a given patient determines every subsequent step, so confirm program type before you schedule.

Check the patient's card first. Original Medicare cards show the Medicare Beneficiary Identifier (MBI) and read "MEDICARE"; Medicare Advantage enrollees carry a plan-specific card from the insurer (Humana, UnitedHealthcare, Aetna, and others). When in doubt, call the eligibility line on the back of the card and confirm program type before scheduling.

Original Medicare's current prior authorization categories, all submitted to your Medicare Administrative Contractor (MAC):

• Certain hospital outpatient department (OPD) services
• Repetitive, scheduled non-emergent ambulance transport (RSNAT)
• Certain DMEPOS items, including specified power mobility devices (CMS maintains and periodically updates the national required-PA list)
• 17 specific services in the six WISeR Model states, effective January 1, 2026 through December 31, 2031

Medicare Advantage sets no single nationwide rule. The vast majority of MA enrollees must obtain prior authorization for at least some services, and specialists, non-emergency hospital care, out-of-network services, and higher-cost procedures are typical triggers. Verify directly with each plan before submitting.

How to appeal a denial

The appeal path differs entirely between Original Medicare and Medicare Advantage. Using the wrong process wastes weeks, because filing at the wrong entry level restarts the clock. Both paths converge at the upper levels (ALJ, the Medicare Appeals Council, then federal court); only the entry point and first two levels differ.

Medicare Advantage (5 levels):

1. Plan reconsideration. The MA plan reviews its own denial. Per CMS guidance, request within 60 days of the denial notice.

2. Independent Review Entity (IRE). If the plan upholds the denial, a CMS-contracted reviewer that operates separately from the plan (Maximus) takes the case. Expedited IRE decisions come within 72 hours; standard decisions within 30 days.

3. ALJ hearing (OMHA). If the IRE upholds the denial and the amount in controversy meets the threshold CMS sets annually, request a hearing before an Administrative Law Judge through the Office of Medicare Hearings and Appeals.

4. Medicare Appeals Council. Part of the Departmental Appeals Board, the Council reviews ALJ decisions.

5. Federal district court. Once the amount in controversy meets the statutory threshold and all administrative levels are exhausted, the case may proceed to federal court.

Original Medicare (redetermination path): for a non-affirmed Original Medicare prior authorization, submit a redetermination to the MAC that issued the decision within 120 days. A Qualified Independent Contractor (QIC) handles the Level 2 reconsideration if the MAC upholds the non-affirmation. Levels 3 through 5 follow the same ALJ/OMHA, Appeals Council, and federal court structure as Medicare Advantage.

What changed for 2026

Three regulatory updates reshape Medicare prior authorization this year. Each is cited and dated.

1. The WISeR Model (effective January 1, 2026)

The Wasteful and Inappropriate Service Reduction (WISeR) Model is a CMS Innovation Center program that introduced mandatory prior authorization for 17 specific services in Original Medicare, but only in six states: New Jersey, Ohio, Oklahoma, Texas, Arizona, and Washington. The model runs through December 31, 2031. Licensed clinicians, not automated systems, issue the final coverage decisions, and inpatient-only services, emergency services, and services that pose substantial risk if delayed are explicitly excluded.

The 17 services include electrical nerve stimulators, deep brain stimulation, epidural steroid injections for pain management, cervical fusion, percutaneous vertebral augmentation, hypoglossal nerve stimulation for obstructive sleep apnea, skin and tissue substitutes, and wound application of cellular and tissue-based products, among others. Providers in these six states should map current CPT/HCPCS codes against the WISeR list before the next billing cycle.

2. CMS-0057-F decision timelines (effective 2026)

The CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) sets mandatory prior authorization decision timelines for Medicare Advantage and other CMS-regulated plans: 72 hours for expedited requests and 7 calendar days for standard requests. Treat those windows as enforceable benchmarks, not acceptable administrative lag. A decision that exceeds the window is a documented compliance issue you can escalate.

3. FHIR Prior Authorization API (required by January 1, 2027)

CMS-0057-F also requires certain CMS-regulated health plans to implement FHIR-based Prior Authorization APIs by January 1, 2027. A FHIR PA API is a standardized interface that lets providers submit requests and receive decisions directly through the EHR, replacing portal and fax workflows. CMS has launched an Electronic Prior Authorization initiative to drive readiness; confirm FHIR API plans with your EHR vendor now, because gaps discovered in late 2026 become scheduling and cash-flow risk in 2027.

Desk-ready submission

Route the request to the right place. Original Medicare and WISeR Model services go to your MAC (not to CMS directly); identify your MAC jurisdiction through the CMS Medicare Administrative Contractor directory, and confirm the current portal before each cycle, with fax as the fallback. Medicare Advantage services go to the individual plan's provider portal, each with its own documentation requirements and turnaround.

Gather the same core data for every submission:

• Medicare Beneficiary Identifier (MBI)
• CPT/HCPCS code(s) for the requested service
• ICD-10 diagnosis code(s) establishing medical necessity
• Complete supporting clinical documentation: progress notes, test results, physician orders, and any plan of care relevant to the service

For Medicare Advantage, request an expedited determination when standard timing would seriously jeopardize the patient's health or ability to regain maximum function, and submit it with the supporting clinical rationale. For WISeR Model services, confirm the current expedited procedure with your MAC.

Documentation is the decisive variable. Insufficient documentation, not fraud, is the leading cause of Medicare improper payments (CMS CERT data). A complete, well-organized record that would support payment after the fact will support prior authorization before the fact; partial submissions produce non-affirmed decisions and force manual back-and-forth that delays care without changing the underlying coverage determination.

How Silna Reduces Denials

Most non-affirmed Medicare prior authorizations trace to two preventable causes: incomplete clinical documentation and submitting to the wrong pathway for the patient's program type. Both are detectable before the request leaves the practice.

Silna Health's Care Readiness Platform automates the workflow end to end: benefits verification, form population, real-time error checking, and multi-channel submission across both Original Medicare MAC pathways and Medicare Advantage plan portals. Silna's Predictive Document Intelligence identifies documentation gaps before submission, targeting the insufficient-documentation failures that drive improper payments rather than genuine coverage disputes. By combining automation with built-in payor communication, Silna cuts pre-visit administrative work by 95%, per Silna Health, 2026.

Silna's strongest adoption is among ABA therapy, physical therapy, and mental health practices, plus care management for older adults and Medicare populations, the practice types where prior authorization volume is highest and documentation requirements are most complex. For teams managing Medicare prior authorization across multiple payers, program types, and the new WISeR requirements, Silna coordinates the full workflow so the first submission is the complete submission. See how it applies to your payer mix at silnahealth.com.

Key terms

Original Medicare (Parts A/B)

Fee-for-service Medicare; requires PA only for a limited, CMS-defined list of services, submitted to the MAC.

Medicare Advantage (Part C)

Private plans that administer Medicare benefits and set their own, extensive prior authorization rules.

MAC

Medicare Administrative Contractor: the regional contractor that processes Original Medicare PA and the Level 1 redetermination.

IRE / Maximus

Independent Review Entity: the CMS-contracted Level 2 reviewer for Medicare Advantage appeals, separate from the plan.

WISeR Model

CMS Innovation Center model adding PA for 17 services in Original Medicare in six states, 2026 through 2031.

CMS-0057-F

The Interoperability and Prior Authorization Final Rule: MA decision deadlines and the FHIR PA API mandate.

Frequently Asked Questions

This article is general educational information, not medical or insurance advice. Coverage rules and clinical criteria vary by plan and state, so consult a licensed healthcare professional or your plan administrator about your specific situation.

About the author

Sagar Jajoo

Sagar Jajoo is Co-founder, Chief Operating Officer of Silna Health, where he's building the first Care Readiness Platform to automate prior authorizations, benefit checks, and insurance monitoring. A UC Berkeley CS and Economics grad, he was previously the first product hire at Truework.

Last reviewed: June 18, 2026.