Guides Fixing lost revenue
10 common claim denials and how to stop them
The short answer
Most claim denials trace back to a handful of steps: eligibility, demographics, authorizations, claim edits and filing deadlines. Fix the step that causes each denial and the same denial stops coming back.
Most claim denials come from a few steps in the workflow, not from bad luck: checking eligibility, entering demographics, tracking authorizations, catching errors before the claim goes out, and filing on time. Working each denial one by one gets the money back on that claim. Fixing the step that caused it stops the next hundred.
This guide lists ten denials that come up again and again, groups them by the step that prevents them, and links each code to its full explanation in denial codes explained.
What the numbers say, and what they don’t
No free public dataset ranks denial reasons for small independent practices. The most recent broad survey is Experian Health’s 2026 State of Claims survey, published October 28, 2026. It asked 204 healthcare professionals responsible for financial, billing or claims decisions (Experian press release). Among the results:
- 75% said claim denials are increasing.
- 40% said their denial rate is above 10% of claims.
- 78% said payer policies change more often than before.
- The causes respondents cited most were services not covered by insurance, missing coverage information, coding errors, changing payer policies and prior authorization issues.
That is a survey of opinions from 204 respondents, run by a company that sells claims software, so treat it as a direction, not a benchmark. Your own remittances are the better source. The ten denials below are the categories that map most directly to a fixable step.
The 10 denials at a glance
| Denial | Codes it usually arrives with | The step that stops it |
|---|---|---|
| 1. Coverage ended or not active | CO-27, CO-26 | Eligibility check before every visit |
| 2. Patient not identified | CO-31, CO-140 | Demographics copied from the card |
| 3. Another payer is primary | CO-22 | Coordination of benefits question at check-in |
| 4. Wrong payer or plan | CO-109 | Eligibility check that names the plan |
| 5. Authorization missing | CO-197, CO-288 | An auth log tied to the schedule |
| 6. Missing or invalid information | CO-16 | Claim scrubber and payer edits |
| 7. Bundled or modifier mismatch | CO-97, CO-4, CO-236 | NCCI and payer edits before submission |
| 8. Not covered or not medically necessary | PR-204, CO-96, CO-50, CO-167 | Benefit check and coverage policy check for planned services |
| 9. Duplicate claim | OA-18 | Claim status check before resending |
| 10. Filed too late | CO-29 | A filing-deadline report worked every week |
Code meanings are from the X12 claim adjustment reason code list as of November 2026.
Before the visit: eligibility, demographics and coverage
Denials 1 to 4 share a root cause: the insurance on file doesn’t match the insurance the patient has on the date of service.
Run an eligibility check before every visit, not just the first one. Coverage changes at job changes, at open enrollment and when Medicaid managed care plans change. The electronic eligibility inquiry (the X12 270, answered by a 271) is one of the HIPAA standard transactions (CMS adopted standards). Most practice management systems can run it in a batch the day before. Look at the plan name and the payer in the response, not just “active”. A patient whose employer plan moved from one carrier to another will show active, at the wrong payer.
Copy demographics from the card, not from memory. CO-31 (patient can’t be identified) and CO-140 (name and ID number don’t match) are almost always typing errors or old data: a maiden name, a missing suffix, a dependent billed under the subscriber’s date of birth. Scan the front and back of the card at every visit where it might have changed.
Ask the coordination of benefits question. “Do you have any other insurance, including through a spouse or parent, Medicare or Medicaid?” CO-22 means the payer thinks someone else pays first. The fix often needs the patient to update their record with the payer, so the front desk should tell them that the same day.
Before the visit: authorizations
Keep one auth log tied to the schedule. CO-197 means the payer has no record of a required authorization. CO-288 means a required referral is missing. Both are prevented the same way: when a service that may need approval is scheduled, someone checks the payer’s list, requests the auth, and records the number, the approved codes, the units and the date range. Before the visit, someone confirms it is still valid. When the claim goes out, the auth number goes on it.
The rules got slightly better in 2026. Since January 1, 2026, under CMS’s Interoperability and Prior Authorization final rule (CMS-0057-F), Medicare Advantage plans, Medicaid and CHIP fee-for-service programs and Medicaid managed care plans must decide expedited requests within 72 hours and standard requests within seven calendar days, and give a specific reason when they deny one (CMS fact sheet, as of November 2026). Commercial plans outside that rule set their own timeframes. Either way, a denial with a reason is easier to fix than a missing auth discovered on the remittance.
When the claim goes out: scrubbing and edits
Use a claim scrubber, and add to its rules. Denial 6 (CO-16) means a field was missing or invalid. X12 requires a remark code with it that names the problem, for example N290 for a missing rendering provider identifier. Every CO-16 you receive is a rule your scrubber should have caught. Add it.
Run bundling edits before the payer does. Denial 7 covers CO-97 (paid as part of another service), CO-4 (modifier doesn’t fit the code) and CO-236 (code pair not allowed together under NCCI). CMS publishes the NCCI procedure-to-procedure edits every quarter (CMS NCCI edits), and most scrubbers load them. Commercial payers publish their own bundling policies.
The fix is not “add a modifier”. CMS’s NCCI manual says a modifier may be used only when the clinical circumstances justify it, never just to get past an edit, and the medical record has to support it (NCCI Policy Manual, 2026, ch. 1). When a scrubber flags a pair, the question for the provider is what the note shows: a separate site, session or problem, or not.
Check coverage for planned services. Denial 8 covers PR-204 (not covered under the plan), CO-96 (non-covered charge), CO-50 (not medically necessary) and CO-167 (diagnosis not covered). For anything scheduled in advance, check the benefit and the payer’s coverage policy, and tell the patient before the visit if it may not be covered. Then the conversation about cost happens before the service, not after the statement.
After the claim: duplicates and deadlines
Check claim status before you resend. Denial 9 (OA-18, exact duplicate) usually means someone resent a claim that was still in process, or sent a correction as a new claim instead of a replacement. A claim status inquiry (X12 276/277), or a look at the payer portal, answers “did they get it?” without creating a duplicate.
Work a filing-deadline report every week. Denial 10 (CO-29) is often final, so it costs the most to get wrong. Deadlines differ by payer and by contract:
| Payer type | Initial claim deadline | Source |
|---|---|---|
| Insurers and HMOs regulated by New York | At least 120 days from the date of service, or longer if your contract says so | NY Insurance Law §3224-a(g) |
| NY Medicaid fee-for-service | 90 days from the date of service, unless a listed delay reason applies | eMedNY General Billing |
| Traditional Medicare | 1 calendar year from the date of service | 42 CFR 424.44 |
As of November 2026. Medicaid managed care and self-funded employer plans set their own limits. The full payer table is in timely filing limits for New York payers.
A deadline report lists every unbilled or rejected claim with its date of service and the payer’s limit, sorted by days left. Rejections from the clearinghouse count: a claim that never reached the payer did not stop the clock. Keep the clearinghouse acceptance report as proof of timely filing.
Track denials by dollars, not by count
A denial log is only useful if it points at a step. For each denial, record the payer, the code pair (group, reason and remark), the dollars, the step that caused it and who owns that step. Once a month, total the dollars by step. The step with the most dollars gets fixed first, even if another step has more denials.
Three habits help:
- Work denials within a set number of days of the remittance. Appeal and reconsideration windows start at the payer’s notice, not when someone gets to it.
- Send the cause back to the person who owns the step. A CO-31 goes to the front desk with the corrected name, not just to the biller.
- Re-check the rule when a code spikes. A sudden rise in one code at one payer often means the payer changed a policy, so read its recent bulletins before you rework the claims.
Five things to do this week
- Export 12 months of remittances (835s) from your clearinghouse or payer portals.
- Total denied dollars by reason code and by payer.
- Pick the top three codes and name the step that causes each.
- Turn on, or check, batch eligibility the day before visits.
- Build a filing-deadline report and put a name on it.
If you’d rather not do step 2 by hand, Marlow’s free billing audit reads your 835s and returns your denials ranked by dollars, with the codes and payers behind each one.
Sources
- Experian Health: 2026 State of Claims survey press release (Oct 28, 2026)
- X12: Claim Adjustment Reason Codes
- X12: Remittance Advice Remark Codes
- CMS: HIPAA adopted standards and operating rules
- CMS: Interoperability and Prior Authorization final rule (CMS-0057-F) fact sheet
- CMS: National Correct Coding Initiative edits
- CMS: NCCI Policy Manual for Medicare Services, 2026, Chapter 1
- New York Insurance Law §3224-a
- eMedNY: Information for All Providers, General Billing
- eCFR: 42 CFR 424.44, time limits for filing claims
General information, not advice on a specific claim, contract or legal question. Rules and rates change; check the linked sources for the current version.