Retroactive Authorization Requests: When a Payer Will Say Yes

There is no national window for a retroactive authorization

Nothing in Medicare sets a deadline for asking a payer to approve a service you have already furnished. What exists is a policy written by each payer, and the ones that publish it set their own terms. Fallon Health allowed one up to 120 days after the date of service, then closed it, a policy choice that binds nobody else. Highmark kept its window open and, from Aug. 1, 2026, capped it at two years.

Medicare Advantage has one federal piece worth knowing, because it decides which process you are in. An organization determination, the plan’s coverage decision, includes the plan’s refusal to provide or pay for a service pre-service or post-service (42 CFR 422.566(b)(3)). A request for payment must be in writing unless the plan has chosen to accept verbal payment requests (42 CFR 422.568(a)(2)). CMS describes the review, not a filing window.

Every row below is language that payer published, and no row in it applies to a different payer.

The four situations a payer will actually review

An emergency has a federal floor under it. A Medicare Advantage plan is financially responsible for emergency and urgently needed services regardless of whether prior authorization was obtained, and it may not instruct members to seek prior authorization for emergency care (42 CFR 422.113(b)(2)(ii)). UnitedHealthcare states in its own Medicare Advantage list that prior authorization is not required for emergency or urgent care (UHC list, effective Apr. 1, 2026). That is UHC’s statement about UHC.

The second situation is a service that could not be foreseen until the procedure was underway. Humana Healthy Horizons in Kentucky lists two versions: the service relates to another that already received prior approval and was not needed when the first one was performed, or the need for the new service was determined during the prior-authorized procedure (Humana policy, April 2024). Louisiana Healthcare Connections allows a review when the physician cannot determine the exact procedure until after it is performed.

The third is a patient who arrived unable to give you what a check requires. Louisiana’s Medicaid policy grants a review when the record documents that the member refused or was physically unable to provide the Recipient ID number. Nevada Medicaid covers the inpatient version: eligibility found during the stay gives 10 business days from that decision, and after discharge 90 calendar days (Nevada Medicaid announcement).

The fourth is a plan whose own policy permits post-service review, and some of those policies are narrow on purpose. Aetna publishes an availability test rather than a deadline: retrospective review is not available for elective services on its precertification lists when precertification did not happen first (Aetna, retrospective review).

The document, the evidence and the fact pattern decide it

Three things decide a retrospective review: the document the payer will accept, clinical evidence measured against that payer’s own criteria, and a fact pattern explaining why prior authorization was impossible. Practices usually get one of the three wrong.

Humana’s Kentucky policy asks for three items: the patient’s name and Humana ID, the authorization number of the related approved service, and clinical information supporting the service. Nevada Medicaid asks for a synopsis of medical necessity for every date of service requested, the records supporting that synopsis, and a discharge summary. Nevada states that voluminous documentation will not be reviewed.

Necessity is measured against the criteria the payer says it applies. Clover Health’s Part C policy states that its utilization management uses CMS criteria, national and local coverage determinations, the plan’s own policies and MCG. A letter that argues the case the way a clinician would, without quoting the criteria the reviewer has to apply, gives that reviewer nothing to approve.

The fact pattern is where documentation written after the fact shows. Louisiana Healthcare Connections will consider a statement that the provider was told no authorization was required, but only when the record gives the date, the time and who gave the information. A note written three weeks later carries less weight.

The time limit is set by the payer, not by Medicare

Every published window here is different, and the differences are not noise. Humana Healthy Horizons in Kentucky allows 12 months when the cause is retroactive Medicaid eligibility and 90 calendar days when the cause is a service related to one already approved. Nevada Medicaid allows 10 business days when eligibility is found during an inpatient stay and 90 calendar days when the finding comes after discharge. Highmark allows two years from the date of service. Fallon Health allows none.

A window can be anchored to a document rather than a visit. Humana counts 90 days from the date of the primary payer’s explanation of payment or authorization denial when that paper shows the service was not covered.

A retroactive authorization request is not an appeal

The two processes answer different questions. A retrospective request asks the payer to decide coverage on a service it has not decided. An appeal asks it to reverse a decision it already made. In Medicare Advantage the first question still runs through the organization determination process, because 42 CFR 422.566(b)(3) includes the plan’s refusal to provide or pay for a service pre-service or post-service. The appeal is a reconsideration, filed within 60 calendar days after receipt of the written determination notice (42 CFR 422.582(b)).

Original Medicare runs a different clock. A redetermination must be filed within 120 calendar days from the date the party receives the notice of the initial determination (42 CFR 405.942(a)). Neither window pauses because a retrospective request is sitting in a review queue.

Filing the wrong one costs appeal rights. Clover Health’s Part C policy states that a retrospective request may be dismissed for untimely notification, and that a contracted provider who furnished a service without prior authorization will not have appeal rights. Humana’s Kentucky policy says a request outside the time frame is denied and ineligible for appeal. Fallon Health allows a provider appeal only for extenuating circumstances.

Tracking that shows whether the payer’s process is real

A retrospective process you cannot measure is a story you tell at a monthly meeting. Log six fields on every request: the date you filed, the date of service, the trigger you claimed, the payer’s decision, the days from filing to decision, and the claim adjustment reason code on whatever came back. That log becomes a grant rate, payer by payer.

The per-payer cut is the only one that means anything, because the policy is per payer. An overall grant rate can hide one payer that approves nine of ten requests and another that dismisses all of them as untimely. CMS’s interoperability rule requires the affected payers to expose prior authorization information through APIs, with operational provisions generally beginning January 1, 2026 (CMS-0057-F fact sheet), so more of that record can be checked against your own log.

Read the refusals together, because the pattern names the fix. Refusals that cite a missing document point at intake. Refusals that reject the trigger point at how the note describes the encounter. A payer that refuses without naming a window or a document is telling you the process does not exist for that service line.

What to fix before the next claim goes out

1. 01

   Give the appeal clock an owner

   One person owns every determination notice date and every payer filing window. A retrospective request filed while an appeal clock runs is how a recoverable claim is lost.

2. 02

   Write the fact pattern at the encounter

   If prior authorization was impossible, the note has to say why while the reason is still in the room: who told the office what, when, and what the member could or could not provide.

3. 03

   Keep the synopsis short and pointed

   Nevada Medicaid states in writing that voluminous documentation will not be reviewed. Lead with the medical necessity of each date of service and attach only the records that support it.

4. 04

   Report grant rate by payer, monthly

   Track filings and grants per payer. The payer with the lowest grant rate is either the one to stop filing with or the file that needs rebuilding.

The filing side of this work lives in prior authorization tracking, and the appeal side of a denial for absent authorization is covered in medical necessity denial appeals. The code definitions on the remittance are in claim denial codes explained. We run both halves through prior authorization services and denial management services.

Questions practices ask us about this