Every September we open the denial aging report for the practices we bill and find the same shape. A cluster of denials from March and April that were touched once, given a status of "pending appeal" and never touched again. A row of CO-197 lines from a payer that changed its authorization rules in the spring. A handful of high-dollar procedures sitting at 150 days with no notes at all. None of it is dramatic on its own. Together it is usually the largest recoverable balance in the practice.
The reason we do this in September and not December is arithmetic. Most commercial appeal windows are 180 days from the remittance date, and Medicare gives 120 days from the date of the initial determination for a redetermination. A denial received in early April runs out of appeal time in early October. If the sweep starts in November, a third of the list is already gone. Start now and most of it is still alive.
Key takeaways
- Pull denials by remittance date, not date of service, and sort by the appeal deadline rather than the dollar amount.
- Every line lands in one of three piles within two touches: corrected claim, appeal with documentation, or write-off with a reason code.
- CO-16 and CO-22 are corrected claims, not appeals; sending them to the appeal queue slows everything else down.
- The write-off reasons, grouped, are the denial prevention plan for the first quarter of 2027.
Pull the list the right way
Do not start from the AR aging report. Aging reports group by date of service, and what matters for a denial is the remittance date, because that is when the appeal clock started. Pull every claim line with a denial adjustment posted between January 1 and June 30 that has no subsequent payment and no corrected claim on file. Export it with the CARC and RARC codes, the remittance date, the billed amount, the payer and the last note.
Then add one calculated column: the appeal deadline. For each payer, take the remittance date and add the appeal window from the contract or the provider manual. Sort by that column, oldest deadline first. This one change is the difference between a sweep that recovers money and a sweep that produces a nice spreadsheet. Sorting by dollar value feels productive, but a $4,000 denial with 90 days left can wait a week. A $380 denial with 9 days left cannot.
The windows are not uniform, and the spreadsheet has to know that. A Medicare Part B denial with a remittance dated April 6 has a redetermination deadline of August 4, so it is already gone by the time a September sweep starts. A commercial denial with the same remittance date and a 180-day contract window is due October 3, which leaves a month. Many Medicaid managed care plans allow only 60 or 90 days, and some commercial contracts negotiated years ago still say 90. Keep a one-page table of appeal windows by payer next to the sweep and update it every time a contract amendment arrives, because the payers do change them.
The codes that are usually worth the effort
| CARC | What it means | Typical fix |
|---|---|---|
| CO-197 | Precertification or authorization absent | Retro-authorization request where the payer allows it; appeal with clinical notes where it does not |
| CO-16 | Claim lacks information or has a billing error | Read the RARC (N-code), correct the claim, resubmit as a corrected claim, not an appeal |
| CO-4 | Procedure code inconsistent with modifier | Coder review; often a missing modifier 25 or 59, or a laterality modifier on a bilateral code |
| CO-50 | Not deemed medically necessary | Appeal with documentation and the payer's own coverage policy quoted |
| CO-22 | Another payer may be primary | Update coordination of benefits with the patient, bill the correct primary, then rebill |
| CO-97 | Bundled into another service | Check NCCI edits; appeal only if a modifier was warranted and documented |
| CO-B7 | Provider not certified or eligible on this date | Credentialing problem; check effective dates and ask for reprocessing once enrollment is confirmed |
CO-29, timely filing, is the code people waste the most time on. Unless you can prove the claim was originally submitted on time (a clearinghouse acceptance report with a date works; a screenshot of your billing system does not), let it go and fix the process that let it age.
The RARC column matters as much as the CARC. A CO-16 with N382 (missing or invalid patient identifier) is a two-minute fix. A CO-16 with N29 (missing documentation) needs the note attached and may need a phone call to learn which note. Two lines with the same CARC can belong in different piles, and the person doing the first pass needs to read both codes before deciding.
Three piles, not one
Once the list is sorted, every line goes into one of three piles within the first pass. We give the team a rule: no line may sit in the sweep for more than two touches without landing in a pile.
- Correct and resubmit. Data errors, missing modifiers, wrong payer, wrong subscriber ID. These are corrected claims (frequency code 7 on the 837, with the original claim number in the payer claim control number field), not appeals, and most payers process them within a couple of weeks.
- Appeal with documentation. Medical necessity, authorization disputes, bundling arguments. Each appeal needs the denial letter, the operative or visit note, the relevant payer policy and a one-page cover letter that says what you want and why. Track the fax confirmation or portal case number on the claim.
- Write off with a reason code. Past the appeal window, below the cost of pursuing, or simply wrong on our side. The reason code matters more than the write-off. "Timely filing, never resubmitted after rejection" is a finding. "Bad debt" is a shrug.
The second pile deserves a cost test. Writing a documented appeal takes an experienced person 30 to 45 minutes once the note is in hand, and a second-level appeal takes longer. A $95 line with a 40 percent chance of overturn is not worth two hours across two levels. Set a floor, in dollars, below which the line goes to pile three with the reason "below appeal threshold", and put the floor in writing so nobody has to defend it line by line.
What a realistic sweep looks like
Here is a worked example built from the shape we see in a typical four-provider orthopedic practice; the figures are illustrative. The practice pulled 412 open denial lines from the first half of the year, totaling about $167,000 in billed charges. After the first pass, 148 lines were corrected claims, 121 were appeals, 143 were write-offs. The corrected claims paid at roughly the contracted rate within three weeks. Of the appeals, a little under half were overturned in the first round over the following two months, mostly CO-197 lines where the payer accepted a retro-authorization and CO-50 lines where the payer's own policy supported the service. The rest went to second-level appeal or were written off with a reason.
The write-off pile is where the practice learned the most. Sixty of the 143 lines were CO-B7 denials for a physician assistant whose enrollment with one plan had lapsed in February and been fixed in May. Nobody had asked the payer to reprocess the claims in between. That is not a denial problem; it is a hand-off problem between credentialing and billing, and the practice fixed it with a single rule: every effective-date letter triggers a reprocessing request.
Notice what the numbers say about effort. The 148 corrected claims produced most of the cash and took the least time per line. The 121 appeals produced the rest and took most of the hours. The 143 write-offs produced no cash and the only durable process change. All three piles were worth working, for different reasons.
Numbers to watch while the sweep runs
We track four things weekly until the list is closed. Lines remaining with fewer than 30 days to the appeal deadline (this should be zero by the end of week two). Appeals filed versus appeals decided, by payer, so a payer that is sitting on appeals gets a status call rather than a second appeal. Overturn rate by CARC code, because it tells you which appeals are worth writing next year and which denials are really coding problems in disguise. And the write-off reasons, grouped, because that list becomes the denial prevention plan for the first quarter.
One more number, tracked once at the end: the share of denied dollars that were recovered, by pile. If corrected claims recover 80 percent of their billed value and appeals recover 35 percent, that ratio tells you where to put the next hire.
The mistakes we see
Practices that treat the sweep as a one-time project. It works as a project once; it works better as a quarterly rhythm where nothing gets older than 90 days without a decision. Practices that appeal everything, including CO-16 data errors that just needed a corrected claim, and then wonder why the payer's appeal queue takes eleven weeks. Practices that let the billing team write off without a reason code because "the codes take too long". The reason codes are the entire point.
The other mistake is honesty related. A denial in "pending appeal" status with no case number and no date is not pending anything. Reset those to open on day one and let the sort order decide what happens to them.
Questions we hear
Should we sweep denials older than the appeal window at all?
Yes, but only to categorize and close them. Some payers accept late appeals with a good reason, and Medicare allows "good cause" for a late redetermination request in narrow situations, but plan for none of it. The value of old denials is what they teach you about the process, not the cash.
Who should run it?
One owner with authority to write off, plus whoever writes appeals. A sweep with five people and no owner produces five spreadsheets. In our own work we assign a single denial lead per practice and give the providers a short weekly list of the notes and letters we need from them.
How long should it take?
The first pass on 400 lines takes an experienced team about a week. Appeals take as long as the payers take, which is usually 30 to 60 days for the first decision and can be longer. If you start in September, most decisions arrive before the holidays.
What to do this week
- Export every denial line with a remittance date between January 1 and June 30 that has no payment and no corrected claim, with CARC, RARC, payer and last note.
- Build the appeal window table by payer from your contracts and provider manuals, and add the deadline column to the export.
- Reset every "pending appeal" line with no case number to open.
- Name one owner, set the dollar floor for appeals in writing, and schedule the first-pass sort for the coming five working days.
- Send providers the list of notes and letters you will need for the CO-50 and CO-197 lines with deadlines in October.
