They Approved It, Then Denied It: Reversing a Retroactive Denial

It's the denial that makes people see red: the MRI was pre-approved, you had it, and months later the claim is denied. The Omnipod and Dexcom your doctor got a prior authorization for get rejected anyway. A rep told you no authorization was even needed, and now there's a bill. You did everything right and the system moved the goalposts. Here's the good news buried in the rage: these are some of the most winnable denials there are, because you're holding the approval.

Why a pre-approved service still gets denied

The fine print almost nobody reads: prior authorization is not a guarantee of payment. Insurers say this in their own documents. Cigna's precertification page states plainly that precertification "does not guarantee payment," and that final payment depends on the services actually provided and the coverage in place when treatment finishes. A prior auth approves medical necessity; when the claim is actually processed, the insurer re-checks eligibility, coding, the dates the auth covered, and plan terms, and can still deny.

The odds are on your side (they count on you not knowing)

The numbers are stark. In Medicare Advantage, insurers made nearly 53 million prior-authorization determinations in 2024 and denied about 7.7% of requests. Only 11.5% of those denials were appealed. But among the ones that were, more than 80% were overturned, fully or partially. Read those together: the system reverses itself constantly when challenged, and relies on the fact that almost nobody challenges.

Step 1: Call and reprocess against the authorization

Before you write any appeal, make one phone call. Have the authorization number and the approval date in hand, and ask the insurer to reprocess the claim against the existing authorization. Many post-approval denials are clerical: the authorization simply wasn't linked to the claim, or the billed codes, dates, or place of service didn't match what was approved. The rep can often fix it on the spot, no appeal needed.

Ask specifically: "There's an approved authorization on file, number ____, dated ____. Please reprocess this claim against it." If an authorization was required but missing, ask whether they'll accept a retroactive authorization. Write down the date, the representative's name, and a reference number for the call.

Step 2: If it stands, appeal with the approval attached

If the denial survives the phone call, file a formal appeal. You generally have 180 days from the denial notice to file an internal appeal, and the clock runs from the denial, not the date of service, so a claim denied months after your care still has a fresh window. For care you've already received, the insurer typically must decide within 60 days.

The centerpiece of this appeal is the authorization itself. Attach the approval letter or number, state that you received the service in good-faith reliance on the insurer's written (or recorded) approval, and ask them to honor it. The full mechanics, the cover letter, the letter of medical necessity, the expedited option, and the independent external review if they say no again, are in the appeal a denial guide.

The paper trail that wins these

Post-approval denials are won on documentation. Build it the moment you get any approval, and demand it when you get a denial:

• The authorization or reference number, the approval date, and the name of whoever confirmed it.
• The specific procedure codes and date range the authorization covers.
• For verbal approvals: insurers record their own calls (that's what "this call may be recorded" means). Ask the rep to document the call in your file and give you a reference number, then, in a dispute, cite the date and time and ask them to pull the recording.
• Copies of every denial notice, appeal letter, and response.

When they retroactively cancel your coverage

A harsher version: the insurer retroactively cancels your coverage and claws back claims. There are limits on this. Under the ACA, rescission (retroactive cancellation) is illegal except in cases of fraud or intentional misrepresentation, and an inadvertent mistake on an application doesn't count. The plan must also give you at least 30 days' advance written notice before rescinding, which is your window to respond or appeal.

Escalating past the insurer

• Fully-insured, individual, or marketplace plans: file a complaint with your state insurance department, which insurers must answer.
• Self-funded employer plans (common at large employers, and outside state jurisdiction): the U.S. Department of Labor's EBSA helps with denied claims; call 1-866-444-3272.
• Persistent bad-faith denials belong with these regulators, and naming that you'll file often moves a stuck claim.