How to Appeal a Prior Authorization Denial: Peer-to-Peer First, Then the Formal Appeal

Direct answer: When a prior authorization is denied, the right sequence is peer-to-peer review first, then internal reconsideration, then a formal internal appeal, then external independent review, and for Medicare Advantage or Medicaid managed care, an administrative law judge hearing if the earlier levels fail. The single biggest mistake is jumping straight to the written appeal, because at some payers filing the formal appeal closes the peer-to-peer window, and the peer-to-peer is the fastest option, a 5 to 15 minute call between the ordering physician and the payer's medical director that does not consume any appeal level. Start by reading the denial letter for the exact reason and the deadline printed on it, then request the peer-to-peer the same day.

STEP ONE: PEER-TO-PEER REVIEW

A peer-to-peer review is a phone call between the ordering physician and a physician reviewer at the insurer, usually the medical director who denied the authorization. It is not counted as an appeal, it does not consume any of the formal appeal levels, and the reviewer on the call has authority to overturn the denial on the spot. The ordering physician should conduct the call personally rather than delegating it to office staff, because most payers require it, and the call is a real-time clinical conversation, not a documentation handoff. Before the call, have the chart open, the treatment rationale outlined, the clinical guidelines nearby, and the denial reason in front of you. If the reviewer on the original denial was not a specialist in the relevant field, ask for one during the peer-to-peer. The request window is short and set by each payer: examples reported by billing guides include 7 calendar days at Cigna's EviCore, 14 days at UnitedHealthcare, and 30 days at Aetna for direct denials, but these vary, so take the window from the denial letter itself. Request the earliest available slot; most payers book within 24 to 72 hours. One caution: the formal appeal deadline keeps running while you wait for the peer-to-peer, so diary it from the denial letter and do not let the call eat the filing window.

STEP TWO: INTERNAL RECONSIDERATION

If the peer-to-peer is not offered, or it fails, the next step is internal reconsideration with new documentation. This is a written submission to the payer asking it to look again, and it should add something the first request did not have: a letter of medical necessity from the treating provider, recent records, imaging or lab results, and the clinical guideline that supports the service. Answer the denial reason line by line rather than restating the diagnosis in general terms. If the denial said the service was not medically necessary, show the guideline and the chart facts that make it necessary for this patient. If the denial said a cheaper alternative should be tried first, show what was tried and what happened. Submit through the payer's portal where one exists, because it creates a timestamped record, and keep a copy of everything submitted.

STEP THREE: THE FORMAL INTERNAL APPEAL

If reconsideration fails, file the formal internal appeal, the first written appeal level, within the deadline printed on the denial letter. Deadlines vary by coverage type: Medicare Advantage appeals are generally due within 60 days, ACA marketplace plans within 180 days, and employer ERISA plans usually within 180 days, but always take the deadline from the letter, not from a general rule. A strong appeal letter includes a direct rebuttal of the payer's stated denial reason, the letter of medical necessity, the supporting clinical records, and the ICD-10 and CPT codes tied to the denied service. For pre-service requests, the payer must generally decide a standard appeal within 30 days and an expedited appeal within 72 hours. If the formal appeal is denied, a second internal level may be available depending on the plan, and for Medicare Advantage a denied first level escalates automatically to the next reviewer.

STEP FOUR: EXTERNAL REVIEW AND BEYOND

If both internal levels fail, request an external independent review. Every non-grandfathered plan must offer it, the reviewer is a physician in the relevant specialty who is not employed by or affiliated with the insurer, and the decision usually binds the insurer. External review is free to the patient, no lawyer is needed, and the request goes through the state insurance department or the instructions in the internal appeal denial letter, generally within four months of the internal denial. For Medicare Advantage or Medicaid managed care, an administrative law judge hearing is the next level after external review where the amount and the rules allow it. Keep every decision letter, because each level's deadline runs from the date on the last decision notice.

THE 2026 RULE THAT CHANGED THE LETTER

The CMS Interoperability and Prior Authorization Final Rule, regulation number CMS-0057-F, took effect on 1 January 2026. For the plans it covers, Medicare Advantage, Medicaid managed care, CHIP managed care, and qualified health plans on the federal marketplace, it cut the standard prior authorization decision window from 14 days to 7 days, set 72 hours for expedited decisions, required payers to state a specific clinical reason for every denial rather than a generic code, and required them to publish plan-level approval and denial statistics. It does not, on its own, reach self-funded employer plans, and it does not cover prescription drugs. The practical effect for a billing team is that denial letters under the rule should now carry a specific reason to answer, so quote that reason back in the appeal and hold the payer to it. Note that no payer publishes a peer-to-peer-specific overturn rate, so treat the peer-to-peer as the fastest option worth trying first, not a guaranteed reversal. Published research on appeals generally, such as the KFF finding that most Medicare Advantage appeals that reach a decision are overturned, describes appeals overall, not peer-to-peer calls, and should not be quoted as a promise for any single case.

WORKED EXAMPLE

An illustrative example, not a real claim. A practice receives a prior authorization denial for an imaging study, with the letter citing a specific clinical reason and a 14-day peer-to-peer window. The same day, the office calls the provider services number on the letter, requests a peer-to-peer review, and diaries the 60-day formal appeal deadline from the letter. The ordering physician takes the call two days later with the chart and the clinical guideline open, explains why the study is needed for this patient, and the medical director overturns the denial on the call. No formal appeal is filed, no appeal level is consumed, and the authorization is in hand within the week. If the call had failed, the next step would have been internal reconsideration with the letter of medical necessity and the guideline attached, filed before the 60-day deadline.

PRIOR AUTHORIZATION DENIAL CHECKLIST

FREQUENTLY ASKED QUESTIONS

A note on codes and coverage: This article is educational information about billing and appeals, not legal or compliance advice. Prior authorization rules, deadlines, and peer-to-peer windows vary by payer, plan, and state, and the CMS rule applies only to the plan types it covers, so always verify them against the denial letter and the payer's policy before acting.

Related reading: Prior Authorization Turnaround Time by Payer · Prior Authorization Process · How to Appeal a CO-197 Denial · Claim Denial Management Workflow · How to Appeal a CO-50 Denial

Part of the complete guide: Claim Denial Codes: The Complete Guide for Medical Billing — every code in this article, explained in one place.