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6 Things Your Health Insurance Company Hopes You Never Find Out About Denied Claims

By Curtis Jones · October 16, 2026

A denial letter from your health plan can feel like the end of the conversation. For a lot of people it is. They pay the bill or skip the treatment.

That is a costly habit. In a January 2026 KFF poll, one-third of insured adults said a health insurer had denied coverage for a service or medication their doctor prescribed in the past two years. Here is what the fine print and the numbers say about pushing back.

Hardly anyone appeals. KFF looked at federal data for HealthCare.gov plans and found insurers denied 19% of in-network claims in 2024. Fewer than 1% of those denials were appealed. Insurers upheld about two-thirds of the appeals they did get, so winning is not guaranteed. But a denial nobody challenges stays a denial.

Many denials are about paperwork, not medicine. In that same KFF analysis, the most common reason insurers gave was simply “Other,” at 36%, followed by administrative reasons at 25%. Only 5% of denials were for lack of medical necessity. If your letter points to a paperwork problem, ask your doctor’s billing office whether the claim can be corrected and sent again.

They have to tell you why, in writing. HealthCare.gov says your insurer must notify you in writing and explain why a claim was denied, within 15 days for a prior authorization request and within 30 days for care you already received. Keep that letter and your Explanation of Benefits. Write down the date, time and name of everyone you talk to.

You have more time than you think. HealthCare.gov says you must file an internal appeal within 180 days of receiving notice that your claim was denied. Medicare Advantage works differently. Medicare.gov says you, a representative or your doctor must file an appeal within 65 days from the date on the initial denial notice. If care is urgent, both systems allow faster decisions.

Your doctor’s letter carries weight. HealthCare.gov suggests sending any extra information you want considered, such as a letter from the doctor. Medicare Advantage numbers show what is at stake. KFF found that in 2024, only 11.5% of denied prior authorization requests were appealed, yet 80.7% of appealed denials were partially or fully overturned. Your state’s Consumer Assistance Program can even file an appeal for you.

The insurer does not get the last word. If the internal appeal fails, you can ask for an external review by an independent third party. HealthCare.gov explains that your insurer is required by law to accept the external reviewer’s decision. You have four months to request it, and the charge is either nothing or no more than $25. In Medicare Advantage, if your plan upholds its denial, Medicare.gov says it automatically forwards the case to an Independent Review Entity.

The process can feel slow, but these rights are built into federal rules. HealthCare.gov says insurance companies in all states must offer an external review process that meets federal standards. Start with the denial letter, call your doctor’s office, and send your appeal before the deadline printed on that notice.

This article is for general information and is not legal or insurance advice. Appeal rules and deadlines vary by plan type and state, so check your denial notice and plan documents, or contact your state’s Consumer Assistance Program or department of insurance for help.