Prior authorization (also called pre-certification or pre-approval) is a determination the payer makes before a service is rendered. When a PA is denied, the payer has concluded in advance that the service may not meet its coverage criteria. That is a different determination — and a different process — than what happens when a submitted claim is denied after service.
PA is not a claims process
A claim denial is made after the service is performed and a claim is submitted to the payer. PA and claims denials have different appeal tracks, different timelines, and require different documents. Treating a PA denial as a claims appeal — or vice versa — means filing to the wrong process and often missing the applicable deadline.
PA approval does not guarantee claim payment.The claim must still meet all other coverage requirements — diagnosis, procedure code, site of service, and benefit limits. Conversely, a PA denial does not always mean the service can't be covered: it can be appealed before the service is performed.
Federal timeline requirements
For ACA-compliant plans, payer response times are governed by 45 CFR 147.136(b)(2):
72 hours
Urgent / expedited PA
When the standard timeframe would seriously jeopardize the patient's life, health, or ability to regain maximum function.
15 calendar days
Standard PA (non-urgent)
The baseline window for prospective (pre-service) authorization requests under 45 CFR 147.136(b)(2).
24 hours
Concurrent review
When coverage for an ongoing service is being reduced or terminated — the payer must notify in advance.
30 days
Retrospective review
From the date the payer receives all required information for the retrospective determination.
Medicare Advantage PA timelines are governed separately by CMS rules. Traditional Medicare Part A/B has limited PA requirements — primarily for certain inpatient admissions and durable medical equipment. ERISA self-funded plans are subject to ERISA's claims procedure rules, which treat PA as an adverse benefit determination with the same internal appeal rights.
Peer-to-peer review
When a PA is denied, most payers offer — and some states require — a peer-to-peer review: a direct conversation between the treating physician and the payer's reviewing physician or medical director. This is one of the most effective tools for overturning a PA denial because it lets the treating physician present the clinical picture directly, without the limitations of a written form.
Request it promptly
Most payers have a short window — 24 to 72 hours — after the denial notice for requesting a peer-to-peer review. Missing that window typically forecloses the option.
Have the clinical record available during the call
The reviewing physician will reference the denial criteria. Being able to point to specific documentation in the chart during the call moves the conversation.
Know what criteria were applied
The denial letter must state the reason and the coverage criteria used. Read it before calling — the peer-to-peer is most effective when the physician can address each criterion by name.
Specialty matching
Some state laws and accreditation standards require that the reviewing physician on the payer's side be licensed in the same specialty or a related specialty for complex cases.
When PA denial leads to a claim denial
When a service is rendered without an approved PA — or after a PA denial — the resulting claim is typically denied for lack of authorization. This arrives as a different denial code (often CO-15 or a plan-specific code) and is generally not appealable on clinical grounds: the procedural requirement wasn't met before service. The exception is emergency services, where federal law limits prior authorization requirements under 45 CFR Part 149 (No Surprises Act) and 42 CFR 422.568 for Medicare Advantage.
Retrospective PA for emergency care
For emergency services, payers cannot require prior authorization before treatment. After the fact, a payer may conduct retrospective review to determine whether the services met the emergency standard. The No Surprises Act (45 CFR Part 149) creates additional protections for patients receiving out-of-network emergency services, including limits on balance billing and requirements for good-faith cost estimates.