What prior authorization actually does and doesn't do

Prior authorization is permission from your insurance company to proceed with a treatment or service, but it does not may provide they will pay for it. Getting prior authorization means the insurer has reviewed your case and determined the treatment meets their coverage rules at that moment. It protects you from being denied after the fact for lack of pre-approval — but it does not lock in payment if your coverage changes, if the provider bills incorrectly, or if the insurer later discovers information that changes their decision.

Think of prior authorization as a green light to move forward, not a promise of payment. The insurer is saying "this treatment is medically necessary according to our guidelines and your current plan." That's different from saying "we will definitely pay this bill when it arrives."

Key Takeaways

  • Prior authorization confirms the treatment meets your plan's medical necessity rules, but does not lock in payment if your coverage ends, changes, or the provider bills incorrectly.
  • Your insurance can still deny payment after prior authorization if the provider uses the wrong billing code, bills out of network, or charges for services not included in the authorization.
  • Prior authorization expires — usually 30 to 90 days depending on the treatment — so a procedure done months later may need re-authorization.
  • If your insurance denies a claim despite prior authorization, you have the right to appeal and can cite the authorization letter as evidence the treatment was pre-approved.

When prior authorization does protect you

Prior authorization protects you from one specific denial: the insurer saying "we never approved this, so we're not paying." Once you have written authorization, that argument is off the table. If the insurer later tries to deny the claim on those grounds, you have a document proving they reviewed and approved it in advance.

This matters because some treatments — specialty procedures, imaging, mental health services, certain medications — require pre-approval under most plans. Without it, the insurer can reject the entire bill. With it, they cannot use lack of pre-approval as the reason.

Reasons an insurer can still deny payment despite prior authorization

An insurer can deny a claim even after issuing prior authorization if the actual bill does not match what was authorized. The most common reasons are:

  • Wrong billing code. The provider submits a code for a different procedure or service than what was authorized. Codes are specific — a code for one type of imaging is not the same as a code for another, even if they sound similar.
  • Out-of-network provider. Authorization for a service does not mean the provider is in your network. If the provider is out of network and your plan does not cover out-of-network care for that service, the insurer can deny it.
  • Services beyond the authorization. The authorization covered one procedure; the provider performed additional services not listed. The insurer will pay for what was authorized and deny the rest.
  • Coverage ended or changed. If your coverage lapses between authorization and the service date, or if you switched plans, the new or lapsed coverage may not honor the old authorization.
  • Insurer discovers new information. Rarely, an insurer will deny a claim if they later learn the patient was ineligible at the time of service — for example, if coverage was terminated retroactively due to non-payment of premiums.

How long prior authorization lasts

Prior authorization is not permanent. Most authorizations are valid for 30 to 90 days from the date issued, though some treatments — particularly ongoing care like physical therapy — may be authorized for longer periods. Check your authorization letter for the expiration date.

If you do not have the service within that window, you will need to request a new authorization. This is especially important for elective procedures or treatments you are scheduling weeks or months in advance. A provider who schedules you six months out should request a fresh authorization closer to your actual service date, not rely on one issued half a year earlier.

What to do if your claim is denied despite prior authorization

If your insurer denies a claim and you have prior authorization, file an appeal when ready. Include a copy of the authorization letter with your appeal. State clearly that the service was pre-approved and ask the insurer to explain why they are denying payment despite that approval.

Many denials despite prior authorization are billing errors — a wrong code, a network status mistake, or a data entry problem. An appeal often catches these. If the insurer denies the appeal, you have the right to request an external review, where an independent reviewer outside the insurance company examines whether the denial was correct. The process and timeline vary by state and plan type, but most external reviews take 30 to 60 days.

How to protect yourself when getting prior authorization

Request prior authorization in writing and keep a copy. Do not rely on a phone call or a verbal confirmation from the provider's office. Ask the insurer directly — call the number on your insurance card — and request that they send you written confirmation. That confirmation should include the authorization number, the service or procedure authorized, the provider's name and credentials, the authorization period, and any conditions or limits.

Before your service, confirm with the provider that they have received the authorization and that they will bill using the exact codes and network status covered by it. Ask the provider to tell you in advance if they plan to bill for anything beyond what the authorization covers. After the service, review your explanation of benefits carefully. If the insurer denies any part of the bill, compare the denial reason to your authorization letter — mismatches are your strongest appeal argument.

Frequently Asked Questions

If I have prior authorization, can the insurer refuse to pay because of a pre-existing condition?

No. If the insurer issued prior authorization, they have already reviewed the treatment and determined it is covered under your plan, regardless of pre-existing conditions. A denial based on a pre-existing condition after prior authorization is a strong grounds for appeal.

Does prior authorization mean the insurer will cover the full cost?

No. Prior authorization confirms the treatment is covered, but your coinsurance, copay, or deductible still applies. You are responsible for your share of the cost. The authorization letter should state your out-of-pocket responsibility, but if it does not, ask the insurer before the service.

What if the provider says they cannot get prior authorization?

You can request it yourself by calling your insurer directly. Providers sometimes say authorization is not available when they mean it is difficult or time-consuming. If the treatment is medically necessary and your plan requires authorization, the insurer must review your request. You may need to provide medical records or a letter from your doctor explaining why the treatment is necessary.

Can an insurer change their mind about prior authorization after I have already had the procedure?

Rarely, but yes. If the insurer discovers you were ineligible at the time of service, or if they uncover fraud, they can deny a claim even after prior authorization. This is uncommon and usually requires evidence of a serious problem. If it happens, you have the right to appeal and request an external review.

How do I know if my treatment requires prior authorization?

Call your insurer or check your plan documents. Most plans require prior authorization for specialty procedures, imaging, mental health services, and certain medications. Your provider's office can also tell you whether authorization is required, but confirm directly with your insurer rather than relying solely on the provider's knowledge of your specific plan.