The appeal system in American health insurance barely gets used. That is the clearest reading of KFF's March 24 analysis of federal claims data from HealthCare.gov marketplace plans: insurers denied an average of 20 percent of claims in 2024 - 19 percent of in-network claims and 37 percent of out-of-network - yet fewer than 1 percent of denied claims were appealed. When consumers did appeal, insurers upheld their original decision 66 percent of the time.
The same report notes that two-thirds of insured adults consider delays and denials by insurers a major problem, and a third say they have personally had a service or medication denied in the past two years. Patients are angry about denials and still not fighting them. The reasons are structural: appeal processes are opaque, deadlines are short, and the individual stakes rarely justify hours on hold. Providers are the only party with both the expertise and the volume to make appeals economical - and even provider organizations appeal only a fraction of what they could win.
What the 20 percent rate hides
Two details in KFF's data matter for billing teams:
- Denial rates vary from 3 to 36 percent in-network by insurer. Same patients, same services, wildly different payer behavior. Your denial rate is partly a payer mix statement, and knowing your per-payer rates is the first step to working them differently.
- The denial reasons are mostly administrative. Where insurers report reasons, 36 percent are uncategorized and 25 percent administrative; only 9 percent are prior-auth-related and 5 percent medical necessity. These are the categories that respond to process fixes, not negotiation.
The picture that emerges is of a system that denies broadly and cheaply, on the safe assumption that almost nothing will be contested.
Both details point the same direction: denial volume is a payer policy choice, while recovery volume is a provider operational choice. The first is set in another building. The second is set in yours.
The economics of appeal participation
Denial recovery follows a participation curve. At low appeal rates, each appeal is expensive because there is no machinery - every case is assembled by hand, and the margin per recovered claim is thin. As participation rises, the fixed costs spread out: templates exist, records-pull workflows exist, deadlines are tracked, and the cost per appeal falls while the win rate holds.
That is why the sub-1-percent appeal figure is best read as an arbitrage opportunity rather than a fact of nature. Claims denied for administrative reasons - a quarter of all denials in KFF's data - are frequently recoverable with a corrected resubmission or a short letter. Most organizations never send either, because nobody is watching that queue at scale.
Provider behavior is the exception worth studying. Where practices work denials systematically - dedicated staff, daily queues, payer-specific playbooks - recovery rates routinely reach a third or more of appealed dollars. The difference between those operations and everyone else is not knowledge or persistence. It is whether the organization treats each denial as a decision to make, or a decision that was already made.
What higher participation requires
- Work every administrative denial the week it lands. These are the cheapest wins in the queue, and they age badly.
- Track per-payer overturn rates. Once you know which payers reverse which denial types, triage stops being guesswork.
- Standardize the first response. A template letter with records attached, filed within days, outperforms the bespoke appeal written three weeks later.
- Escalate what you win. External review exists precisely because internal appeals get upheld 66 percent of the time. The next level is a different decision-maker.
The takeaway
A 20 percent denial rate with a 1 percent appeal rate is not a system in equilibrium - it is a system being exploited by whoever shows up. Providers who build appeal machinery convert payer noise back into revenue, claim by claim. The constraint is labor, which is why we keep making the same argument in these posts: the queue has to be worked by something that never gets tired of it. QHB's agents read every denial, draft the response, and file before the deadline, so the 99 percent of unappealed claims stops being the industry's quiet tax on your bottom line.