Can You Get a Prior Authorization After the Service Was Provided?
Sometimes, and only where the payer's own provider manual allows it. For an emergency stay the better question is whether authorization was required at all, because federal rules bar plans from requiring it before emergency services.
Written by Salman Saeed, CEO and Co-Founder · Reviewed by a Certified Medical Coder · 
In short: retro authorization is a payer policy, not a right. Emergency care needs no authorization under federal rules, so a CO-197 on an emergency stay is usually a notice or appeal question. For other services, find the retro window in the payer's manual and send the request inside it.
Can You Get a Prior Authorization After the Service Was Provided?
Sometimes, and only where the payer's own provider manual allows it. Each payer sets its own retro window in its manual or contract, so the answer is a clock in a document, and for emergency care the first question is whether authorization was ever required.
Three situations come up on a denied claim. They need different fixes, so sort the account before anyone phones the payer.
| Situation | What usually applies | First move |
|---|---|---|
| Emergency stay or emergency visit | No authorization was required. The payer may still want notice of the admission. | Check the notice rule, then appeal or correct the claim |
| Urgent service done after hours | The manual may allow a retro request with a short deadline | Find the section and send inside its clock |
| Planned service done with no authorization | The manual decides, and some payers allow only an appeal | Read the denial letter and the manual before choosing |
A prior authorization is the payer's approval before a service. The prior authorization explainer covers the basics, so this post sticks to the late request.
Did an Emergency Stay Need Prior Authorization at All?
No. Under 45 CFR 149.110(b)(1), a plan or issuer that covers emergency department services must cover emergency services without the need for any prior authorization determination, even when they are provided out of network. For Medicare Advantage, 42 CFR 422.113(b)(2)(ii) makes the plan financially responsible for emergency and urgently needed services regardless of whether there is prior authorization.
Care after the patient is stable is a narrower question. Post-stabilization items and services stay inside the emergency definition unless every condition in 45 CFR 149.410(b) is met, which the post-stabilization notice and consent post walks through.
EMTALA points the same way at the front door. The EMTALA and billing rule explains that insurer authorization cannot be sought until after the screening exam and the start of stabilizing treatment.
So a CARC 197 on an emergency claim is not a retro request waiting to happen. X12 words CARC 197 as precertification, authorization, notification or pre-treatment absent, and the payer may be applying a notice rule under that wording. Read the remark code on the CO-197 page, then check the notice clock in the next section.
What Do Payer Manuals Say About Late Notice and Retro Requests?
They say different things, and the differences are the whole job. The table pulls the wording from two payer manuals and the Medicare rule. Treat it as a map to the right section, not a substitute for the manual that applies to your contract.
| Payer or program | What the manual or rule says | Where |
|---|---|---|
| UnitedHealthcare, emergency admission | Notify within 24 hours, or the next business day on a weekend or holiday, from the time coverage information is known. State the extenuating circumstances. Payment is not reduced for a notification delay in an emergency. | 2026 Care Provider Administrative Guide, ch. 7, p. 93 |
| UnitedHealthcare, clinical review of the notice | UnitedHealthcare decides within 1 business day of receiving complete clinical information. If complete information is not received within 3 business days, the case is denied for lack of information. | Same section, p. 93 |
| UnitedHealthcare, late notice that is not an emergency | If notice is late but within 72 hours of admission, the reduction is 100% of the average daily contract rate for the days before notice. After 72 hours, or with no notice, it is 100% of the contract rate for the whole stay. | Ch. 7, p. 94 |
| UnitedHealthcare, urgent cardiology and advanced imaging after hours | Request a retrospective review within 2 business days of the date of service for stress echocardiograms and advanced outpatient imaging, or within 15 calendar days for diagnostic catheterizations and electrophysiology implants. | Ch. 7, pp. 104 to 105 and 108 |
| Aetna, any inpatient admission | Notify Aetna of all inpatient admissions, including those through the emergency department, within two business days of the admission. | Aetna Office Manual, p. 33 |
| Original Medicare, outpatient prior authorization list | The request must be submitted before the service and before the claim, and the claim is denied without a provisional affirmation. | 42 CFR 419.82(b)(1), (c)(1)(ii) |
The UnitedHealthcare guide excludes some plan types from its admission protocol, such as Medicaid and CHIP plans, so confirm the member's plan is one the guide governs.
Aetna's manual adds that if a patient cannot give coverage information, you must contact Aetna as soon as you become aware of the coverage and explain the extenuating situation when you notify. UnitedHealthcare's cardiology protocol also says the documentation must explain why the procedure was urgent and why no authorization number was requested in normal business hours.
How Do You Request a Retro Authorization, Step by Step?
- Read the remit. The CARC and any remark code, such as M62 for a missing or invalid treatment authorization code or N54 for claim information inconsistent with the authorized services, show whether the payer found no authorization or a mismatch.
- Confirm what was required. Check the payer's authorization list for that date of service and plan. The service may have needed only notification, or nothing.
- Find the retro rule in the manual. Write down the deadline, the channel and who decides. If the manual has no retro rule, the route is the appeal in the denial letter.
- Build the packet from the list below and attach the denial.
- Send it through the channel the manual names. UnitedHealthcare says prior authorization requests go in electronically, not by phone or fax, except where law requires, but its after-hours cardiology and imaging retro reviews are phoned in, so use the channel in the section that applies.
- Record the reference number. Aetna says a reference number is not an approval, and UnitedHealthcare says the same of its service reference number, so do not treat either as authorization.
- Calendar the decision follow-up and the appeal deadline, because a retro request does not stop the appeal clock.
What Goes in the Packet?
- The ED record with arrival time, triage and the screening exam, or the order and time for a direct admission.
- A physician statement of why the service was urgent, and why no request was made before it.
- The registration log showing when coverage information became known and who found it.
- The admission order and the clinical notes that support medical necessity against the payer's criteria.
- Time-stamped proof of every notice or call, including the reference numbers.
- The denial or remit that started the review.
What Does a Late-Notice Case Look Like with Dates?
A patient is admitted through the emergency department on Friday, March 5, 2027, unconscious and with no insurance card. Registration finds an Aetna plan on Saturday. Under the two business day rule, notice is due by Tuesday, March 9.
The notice went in on time, so a later authorization denial is a payer error to appeal with the time stamps.
What If the Payer Will Not Issue a Retro Authorization?
Appeal, and lead with the facts the payer's own rule asks for. If the claim is an inpatient stay billed to Medicare, the admission is judged under the two-midnight rule, not an authorization. For a Medicare Advantage plan, 42 CFR 422.138(c) says a plan that approved a service through prior authorization may not later deny it for lack of medical necessity, so get the approval in writing when you have it.
If the stated reason is medical necessity rather than a missing authorization, the appeal changes. The CO-50 appeal post and the peer-to-peer preparation post cover that route. The denial management playbook sets the order of work across all of these.
Do not bill the patient while this is open. UnitedHealthcare's guide says a facility may not bill the member for noncompliance with its notification protocols, and Aetna's manual says you may not bill or balance bill members when a claim is denied for administrative reasons such as lack of a required referral or authorization.
How We Handle Retro Requests
For internal medicine groups and hospitalists who admit through the ED, we find the payer's retro policy and deadline in its provider manual, then send the request with the records for the stay and the reason no authorization was obtained. Authorization denials are worked within 48 hours. See the prior authorization service, the internal medicine billing page or book a call.
- 45 CFR 149.110 Preventing surprise bills for emergency services · eCFR
- 42 CFR 422.113 Special rules for emergency and urgently needed services · eCFR
- 42 CFR 422.138 Prior authorization · eCFR
- 42 CFR 419.82 Prior authorization for certain hospital outpatient department services · eCFR
- 2026 UnitedHealthcare Care Provider Administrative Guide, chapters 7 and 15 · UnitedHealthcare
- Aetna Office Manual for health care professionals · Aetna
- Claim adjustment reason codes · X12
- Remittance advice remark codes · X12
We check every rule, code and deadline against the official source. See our editorial policy.
Common Questions
Straight answers from the team that does the work.
Ask a billing lead directly. A 20-minute call, Monday to Friday, 9am to 5pm Eastern.
01Can you get a prior authorization after the service was provided?
Sometimes. It depends on the payer's provider manual, since each payer sets its own window. UnitedHealthcare, for example, allows after-hours retrospective reviews for urgent cardiology and advanced imaging within set days. Emergency care needs no authorization, so check the notice rule instead.
02Does an emergency admission need prior authorization?
No. 45 CFR 149.110(b)(1) requires plans to cover emergency services without any prior authorization determination, even out of network, and 42 CFR 422.113 applies the same idea to Medicare Advantage. The payer may still require notice of the admission, which is a separate clock in its manual.
03How soon must a hospital notify the payer of an emergency admission?
It depends on the payer. UnitedHealthcare's 2026 guide says within 24 hours, or the next business day on a weekend or holiday, from the time coverage information is known. Aetna's manual says within two business days of the admission. Confirm the clock in your contract and manual.
04Can the patient be billed if the payer denies retro authorization?
Not in the cases the two manuals address. UnitedHealthcare says a facility may not bill the member for its own noncompliance with notification protocols, and Aetna says you may not bill or balance bill members for administrative denials such as a missing authorization. Check your contract before any patient statement goes out.
Talk to a Billing Lead.
A 20-minute call about your payers, volume and setup. Monday to Friday, 9am to 5pm Eastern.