When There Are Hundreds of Claims, the Arithmetic Changes
Physicians and practices initiated 1,049,137 federal IDR disputes in the second half of 2025 and facilities 323,249 more, against 177 initiated by health plans and issuers. This page is about what the published data says once the number of claims stops being small — which band of filer actually files most, where disputes die at scale, and which published figure stops being the right one to plan against.
The Biggest Filers Are Not the Biggest Organisations
| Staff of the initiating party | Disputes initiated | Share of all initiations |
|---|---|---|
| Fewer than 20 | 140,185 | 10.2% |
| 20 to 50 | 416,179 | 30.3% |
| 51 to 100 | 137,103 | 10.0% |
| 101 to 500 | 215,470 | 15.7% |
| More than 500 | 154,282 | 11.2% |
| Size not reported | 287,952 | 21.0% |
| All initiations | 1,372,563 | 100% |
Source: CMS, Federal IDR Supplemental Tables, Q3 and Q4 2025, Table 2. Size is not reported for 287,952 initiations, so read the distribution as directional. CMS publishes these tables here.
The largest known band is 20 to 50 staff, with 416,179 disputes — 2.7 times what parties with more than 500 staff filed. Groups in the middle of the distribution are the most common filer in this process, not the exception squeezing in at the margins.
That matters for how the question is usually framed. The barrier to disputing a backlog has never been headcount. It is the cost of preparing each filing, which is what batching and the administrative fee cut of June 2026 changed — what the 2026 rule actually did.
One Closed Dispute in Five Never Reached a Decision
| How the dispute closed | Disputes | Share of closed |
|---|---|---|
| Payment determination issued | 1,145,039 | 79.0% |
| Found ineligible | 271,399 | 18.7% |
| Closed for other reasons | 33,462 | 2.3% |
| All closures | 1,449,900 | 100% |
Source: CMS Table 5, Q3 and Q4 2025. Eligibility was challenged by the non-initiating party in 574,128 of the 1,372,563 disputes initiated — 42%.
At one filing a week, a 19% ineligibility rate is a nuisance. At a hundred filings a month it is the largest single loss in the operation, and unlike the merits it is entirely inside your control: the wrong forum, a missed window, a service the protections do not cover. What eligibility turns on.
The routing question underneath most of it is plan type, because ERISA prevents states from regulating self-funded employer plans. Self-funded plans were 936,930 of the 1,372,563 disputes initiated — 68% — and state and local government plans, which ERISA does not reach at all, another 100,271. How the plan-type split differs by payer.
85% Is Two Different Figures
| Measure | H1 2025 | H2 2025 |
|---|---|---|
| Headline win rate, all determinations | 88% | 85% |
| Share decided by default | 22% | 17% |
| Of those defaults, share to the provider side | 91% | 90% |
| Win rate excluding defaults | 87% | 84% |
Source: the Departments' report text for the second half of 2025, which states these shares directly.
A default decision is one where a party failed to submit an offer or pay its fees; the certified IDR entity is then required to rule for the party that did, without reaching the merits. 17% of determinations ended that way, and 90% of those went to the provider side. Strip them out and the contested win rate is 84%, down from 87% six months earlier.
For a filing operation this cuts in two directions at once. The favourable direction is that a meaningful share of disputes is decided because the payer did not participate. The unfavourable one is the mirror image: every deadline your own operation misses converts a live claim into that same statistic, for the other side. At volume, calendar discipline is not administration — it is the win rate.
The Widest Gaps Sit on the Smallest Claims
CMS publishes the median prevailing offer as a share of the plan's own qualifying payment amount, broken out by claim size. In the fourth quarter of 2025 it ran 5.22× the QPA on claims under $100 and 1.69× at $10,000 and above. Claims under $500 accounted for 72% of all payment determinations in the half-year.
That is the inversion worth naming: the claims with the widest proportional gap are the ones a busy operation triages away first, because each is small in absolute dollars. The arithmetic of whether they are worth filing is on the calculator, and the full table by claim size and by specialty is on the data page.
All of these figures are available as JSON and CSV if you would rather run the arithmetic against your own claim mix than read ours.
Common Questions About Filing at Volume
Does federal IDR only make sense for large organisations?
The published filing data says no. CMS breaks initiating parties down by staff size, and the largest known band in the second half of 2025 was 20 to 50 staff, with 416,179 disputes initiated — 2.7 times as many as parties with more than 500 staff. Size is not what decides whether the process is worth using; the per-dispute cost of preparing a filing is.
What actually kills disputes at volume?
Eligibility, not the merits. Of the 1,449,900 disputes closed in the second half of 2025, 271,399 — about 19% — were closed as ineligible and never reached a decision, and the non-initiating party challenged eligibility in 574,128 of the 1,372,563 disputes initiated. At one filing a week that is an annoyance. At a hundred it is the dominant loss, and it is the part a documented intake process can actually change.
Is the headline win rate the number to plan against?
Not on its own. 17% of payment determinations in the second half of 2025 were default decisions — one side failed to submit an offer or pay its fees, so the certified IDR entity was required to rule for the other without reaching the merits — and 90% of those went to the provider side. Excluding them, the provider win rate was 84%, against a headline 85%. At volume the forfeit rate cuts both ways: a missed deadline on your side converts your own claim into the same statistic, in the payer's favour.
Why do small claims matter more at volume than they look?
Because the multiple runs the other way from the dollar amount. CMS Table 13 puts the median prevailing offer at 5.22× the plan's qualifying payment amount on claims under $100 in the fourth quarter of 2025, falling to 1.69× at $10,000 and above. Claims under $500 accounted for 72% of all payment determinations in the half-year. Those are precisely the claims a busy operation writes off.
Who does Proprius Recovery actually work with?
Out-of-network physicians and physician practices. We are not a law firm, we are not a medical practice, and we do not represent hospitals or facilities. Facilities file their own disputes and appear in the federal data as their own category — they initiated 323,249 of the 1,372,563 disputes in the second half of 2025. The process mechanics described on this page are identical for both, which is why the page exists; the engagement is not.