White paper · Denial management operations

The denial management worklist: code to root cause, root cause to owner, owner to deadline

Short answer: an 835 says why a line was not paid in two code sets and a group code; most worklists stop there and sort by age. The map we run in Work Genie resolves every CARC and RARC pair to a root cause, each root cause to a named owner, each owner to a deadline the payer enforces, including what the October 1, 2026 update changed.

CR 14492 · effective Oct 1, 2026 N923 to N940 · start Jul 1, 2026 297 of 297 CARCs · categorized Route on the CARC and RARC pair

October 27, 202614 min readASP-RCM Solutions

Edition

White paper · 2026

Focus

Denial worklist

Codes

297 CARCs · N923-N940

Metric

Capture efficiency

Effective date

Oct 1, 2026

Length

14 min read

Oct 1, 2026

Effective date of the CARC and RARC update loaded by CMS CR 14492 [1]

18new RARCs

N923 to N940, July 1, 2026 start date on the X12 list [3]

297of 297

Active CARCs mapped to a denial category in the Work Genie reference master

47%

Capture efficiency on one spreadsheet-run FQHC worklist, 2026, before our team took the work

Why most denial worklists fail

Effort without a map, measured on two books

One job: the right line in front of the right person before the clock runs out. Neither book below lacked effort; both lacked a map from the code to a person and a date.

Spreadsheet-run AR worklist, one multi-site FQHC book, 2026

Diagnostic, before our team took the work.

47%real work

Capture efficiencytouches that changed claim state

53%tags and notes

Tags, notes, hand-offsno state change

Real workTags, notes and hand-offs

$139K parked

Internal hand-offs between teams on that FQHC book, no owner, no deadline

1,059 touches

Logged on lines under $100 while higher-value denials aged

4.3 touches per claim

Hospital book, every account worked, yet $490K untouched for more than 60 days

0 lines

On either book carrying a named owner and a payer-derived due date

Where 100 worklist accounts go when triaged by recoverable dollars

From the AR Workflow Engine page.

Paid or in payer commitment within seven daysof 100 accounts

4747%

Routed upstreamthe root cause was never an AR problem

1616%

Still in follow-upremaining

3737%

Resolved in seven daysUpstream ownerFollow-up

What the 835 actually tells you

Three layers on every adjusted line, and two facts that shape every rule

Group code, CARC, RARC [2] [3]; see the 835 ERA glossary entry. A CARC may require a remark code, so the same CARC with different RARCs means different work; and codes carry stop dates, so a rule keyed to CARC 15, 138, 165 or 168 (stopped 2018) never fires [2].

Layer	Values	What it tells the worklist
Group code	CO contractual, PR patient, OA other, PI payer-initiated (CR unused from 5010)	Who owes the money: payer, patient, or nobody
CARC	16, 18, 29, 45, 50, 97, 197; newest 308, start November 1, 2025	Why the line was paid differently from the way it was billed
RARC, supplemental	M and N series, for example N4, N130, N936	Explains an adjustment a CARC already describes
RARC, Alert	Codes prefaced with Alert, for example N938, N939	Processing information, never tied to an adjustment

The October 1, 2026 update

The code update cycle behind CR 14492

Three updates a year, about March 1, July 1 and November 1. Transmittal 13791 loads the July 1 lists: effective October 1, implemented October 5 [1]. It lists no codes; contractors pull them from X12 and stop reporting deactivated codes, except on COB and reversal claims adjudicated before the deactivation [1].

1
Mar 1, 2026X12 list: N917 to N922 start; N386 modified
2
May 27, 2026CMS issues CR 14492 [1]
3
Jul 1, 2026X12 list: N923 to N940 start [3]
4
Oct 1, 2026Effective for Medicare contractors, by date of service
5
Oct 5, 2026Implementation date
6
About Nov 1, 2026Next X12 publication; next CMS update follows

Diff your rules

Week of publication

Denials arrive

New codes on the 835 from October

Next diff

November

Regression-test the worklistCodes live on remittances

What moved

RARCs with a July 1, 2026 start date, and the four that change routing

Code [3]	Description (paraphrased)
N923	Not denied; the MAO made a payment responsibility determination (encounter data)
N924	Pending, not denied; MAO had not yet determined payment responsibility
N925	Denied; MAO found no payment responsibility
N926	Partially denied; MAO found no payment responsibility for some service lines
N927 to N934, N940	Missing or invalid x-ray, bitewing or periapical x-ray, photo, quadrant identifier, pre- or post-operative images, full mouth x-ray
N935	Alert: patient is no longer a Medicaid or Qualified Medicare Beneficiary
N936	Service code is the secondary or tertiary procedure subject to the Medicare Multiple Procedure Payment Reduction rule
N937	Service line denial threshold exceeded: a payer-level pattern to escalate, not a line to fix
N938	Alert: do not resubmit; the claim will be reprocessed, so a rule that queues every zero-paid line for rework creates duplicates
N939	Alert: you may contact the payer for a peer-to-peer review, which belongs to the clinical appeal owner
N921 March list	Reconsideration or appeal time limit has expired: a write-off review, not an appeal task

What it broke

Six worklist rules the 2026 lists break, and the fix

Old rule	Why it breaks [2] [3]	Fix
Queue every zero-paid line for resubmission	N938 lines will be reprocessed by the payer	Hold N938 lines 30 days, then check the reprocessed 835
Appeal every CO denial over a dollar threshold	N921 says the appeal window is already closed	Route N921 to write-off review with the reason captured
Route medical necessity denials to the appeal writer	N939 adds a peer-to-peer path	Route CO-50 with N939 to the clinician owner first
Treat denial counts per payer as noise	N937 flags a service-line denial threshold	Open a payer escalation task on the first N937
Route on CARC 15, 138, 165 or 168	Deactivated since May 1, 2018	Retire the rule; map the replacement codes
Ignore encounter remarks	N923 to N926 are MAO determinations on encounter data	Separate encounter responses from provider claims

Every code update is a regression test for your worklist: diff your rules the week the list publishes, not the month the denials arrive.

Step one: code to root cause

From code pair to root cause, selected rows from the reference master

A root cause is the upstream failure the owner can fix. The same CARC can have different root causes, which is why the RARC and the payer matter.

Group and CARC [2]	Typical RARC [3]	Root cause	Category
CO-16 claim lacks information	N4, M51, N130	Registration or charge data incomplete or invalid	Front-end data
CO-197 precertification or authorization absent	N54, payer-specific	No authorization on file for the service or units	Authorization
CO-50 not medically necessary	N115, N939	Documentation below coverage criteria; peer-to-peer may be offered	Clinical and coding
CO-18 duplicate claim or service	N522	Resubmitted without correction; sibling claim already paid	Follow-up discipline
CO-29 timely filing limit expired	N211	Claim or correction not submitted inside the payer window	Follow-up discipline
CO-109 or CO-22 not covered by this payer, coordination of benefits	N104, N130	Wrong payer, wrong order of benefits, eligibility not verified	Eligibility
CO-4 or CO-11 modifier or diagnosis inconsistent	M20, N657	Coding edit failure; NCCI or payer policy	Coding
CO-97 included in another service	M15, N19	Bundling, unbundling or missing modifier	Coding
CO-B7 or CO-185 provider not certified or not eligible for this service	N570, payer-specific	Rendering or billing provider not enrolled for the service	Credentialing
CO-45 charge exceeds fee schedule	N381 and contract remarks	Contractual; investigate only if the allowed amount is below contract	Contract variance
PR-1, PR-2, PR-3 deductible, coinsurance, copay	N-series patient remarks	Patient responsibility; statement, not appeal	Patient

CO-45 charge exceeds fee schedule

Looks like a denial, is not

Contractual adjustment
Close unless allowed is below contract; then contract variance

PR-1, PR-2, PR-3

Looks like a denial, is not

Patient responsibility
Statement and estimate workflow, never an appeal

CO-18 duplicate claim

Looks like a denial, is not

Someone already resubmitted
Find the sibling claim; do not send a third copy

The reference master

What the map is built on, and how often it is re-tested

Reference master and the predictor that shares it

The worklist and the Denial Prediction Engine share one code map, so each update loads once.

CARCs mapped to a denial categoryafter the rebuild

297 of 297100%

Before the rebuildof 297

279%

RARC rows loadedwith 8,623 HCPCS and 74,719 ICD-10

1,137100% of the list

Payer-specific CARC patterns, pre-submissionDenial Prediction Engine

80pattern library

First-pass denial ratebefore submit-gate scoring

12.4%baseline

Two quarters laterdenials written back against their score

8.2%-34%

AfterBeforeLoadedPredictor

Step two: root cause to owner

Root-cause category to owning station, and the exception that opens

An owner is a role with authority to fix the upstream cause, not whoever works AR that day. The RCM Command Center names ten stations; the denial map routes into six. If two teams can claim a denial, neither owns it: in Work Genie a line has one owner and a hand-off is a timestamped event.

Category	Owning station	Exception queue	Preventive control
Eligibility and coordination of benefits	Eligibility and VOB	Coverage conflict	270/271 before the visit; eligibility engine
Authorization	Authorization	Units low, expiring or absent	Auth ledger with end dates; payer form library
Front-end data	Charge capture and claim edits	Edit fails twice	Registration validation; pre-submit scrubbing
Coding	Coding	Query to provider	Submit-gate edits; denial prediction
Credentialing	Credentialing	Provider not enrolled for payer or service	Enrollment status on the claim before release
Follow-up discipline	Denials and A/R follow-up	No next action set	Deadline-first ranking; one owner per claim

Step three: owner to deadline

The yield rank Work Genie applies to every denied line

The deadline is the payer’s: the appeal window, the filing limit for a corrected claim, the age at which a payer stops responding. See the timely filing clock case study and the denial yield model.

1
Expected $Allowed times recovery probability
2
EffortTouches and records to win
3
DeadlineDays left on the payer clock
4
Yield rankWork this line next

Supervisor

Allocates the ranked work; a caller cannot pick the easy lines

Caller

One touch = one submitted record

AllocationExecution

Deadline rules by root cause

Which clock governs, and the default due date

Category	Clock that governs	Default due date in the worklist
Front-end data, eligibility, coding	Payer timely filing limit for a corrected claim	Correction submitted at least 14 days before the filing limit
Authorization, medical necessity	Payer appeal window from the remittance date	Appeal or peer-to-peer inside the window; first touch within 5 business days
Credentialing	Enrollment effective date and the filing limit	Release the day enrollment posts; escalate if the filing limit is inside 30 days
Duplicate, contractual, patient	None; these close	Close with reason the same day
N938 do not resubmit	Payer reprocessing	Review the reprocessed 835 at 30 days

1 touch

Equals one submitted record with the action, outcome and next date; notes do not count

12 checks

Transaction audit applied to every submitted record

24 hours

QC service level on sampled records across every organization

Supervisor

Allocates the ranked worklist; callers do not self-select

Running the map in Work Genie

From 835 to closed line, five stations

Work Genie, the ASP-RCM AR and denial work-allocation platform, runs across more than two dozen client organizations on two live servers; the map is configured as reference data and routing rules, not a procedure document.

1
Ingest835 posts line by line
2
ResolveCARC and RARC pair to category
3
RouteOwner, queue, deadline
4
WorkOne submitted record per touch
5
Audit12 checks, QC in 24 hours

Reference master

297 CARCs, 1,137 RARCs with dates

Routing rules

Category to station to clock

Workflow, server-side

One owner per line; hand-off is a timestamped event

DataRulesPeople

Platform facts behind the map

Operational facts and labelled tests

Fact	Status
297 of 297 CARCs and 1,137 RARCs in the reference master; 86,000 rows load in 1.67 seconds	Operational July 2026
All claim work through the workflow server-side; one owner per line; QC users in 22 organizations	Operational October 2026
Prior-authorization form library: 952 rows, about 302 payers, 98 portal-only; 4 of 5 in-house forms it replaced were outdated	Operational October 2026
Load test: 100 simulated callers, 45,900 claims at 30.4 per second; 25 simulated QC auditors, 36,700 verdicts; zero failures	Internal test synthetic data, not a client result
Scale test: all endpoints under 60 ms at 90,000 claims after trigram indexes	Internal test synthetic data, not a client result
Release gate: 704 of 704 page walks, 11 roles, 1,191 unit and 1,388 integration tests	Internal October 2026

A 90-day build plan for your own map

From 835 export to a worklist with owners and deadlines

No platform required: 12 months of 835s, your payer contracts and a decision about owners.

1
Days 1 to 30Export distinct CARC, RARC and group code combinations from 12 months of 835s; rank by denied dollars; retire rules on deactivated codes
2
Days 31 to 60Map the top combinations to root cause and owner; load payer appeal and filing clocks; set default due dates
3
Days 61 to 90Switch on supervisor allocation and the one-touch-one-record rule; start QC sampling; publish the first denial yield report

Codes

Export, rank, retire

Owners and clocks

Map, load, set

Discipline

Allocate, audit, report

Month oneMonth twoMonth three

KPIs the worklist reports weekly

Measure owners and deadlines before recoveries

KPI	Definition	Why it matters
Lines without an owner	Open denied lines with no assigned station	Zero is the only acceptable number
Lines inside 14 days of a payer deadline	Count and dollars by owner	The work that cannot wait until Monday
Capture efficiency	Submitted records that changed claim state, over all records	47 percent was the spreadsheet baseline on one book
Yield per touch	Expected recovery divided by submitted records	Sorts the queue; denial yield model
Upstream route rate	Denials returned to eligibility, authorization, coding or credentialing	The number that shrinks next month’s denials
QC verdicts inside 24 hours	Sampled records audited within the service level	Quality is asserted by the auditor, not the caller

Takeaway

A worklist that does not carry an owner and a deadline is a report. The remittance already contains everything needed to assign both; a recovery without them is luck.

What to do this week

Six moves before the November list

Export the distinct code combinations from 60 days of 835sCARC, RARC and group code, with denied dollars behind each.

Retire every rule keyed to a stop-dated codeCARC 15, 138, 165, 168 and anything else with a stop date on the X12 list [2].

Write the four routing rows for N938, N939, N937 and N921Hold, clinician, payer escalation, write-off review.

Name one owning station per categoryEligibility, authorization, front-end data, coding, credentialing, follow-up.

Load payer appeal and filing clocks as due datesCorrection 14 days before the filing limit; first appeal touch within 5 business days.

Run the diff again the week after November 1Or let the free denial audit run your last 90 days of 835s through the same map and return the owner and deadline distribution.

FAQ

Frequently asked questions

What is the difference between a CARC and a RARC?

A Claim Adjustment Reason Code explains why a claim or service line was paid differently from the way it was billed, and it always travels with a group code such as CO, PR, OA or PI that assigns responsibility for the adjustment. A Remittance Advice Remark Code adds detail: supplemental RARCs explain an adjustment a CARC already describes, and Alert RARCs carry remittance processing information and are never tied to a specific adjustment.

When do CARC and RARC lists change?

X12 publishes updates three times a year, around March 1, July 1 and November 1. CMS then issues a recurring change request telling Medicare contractors to load the new, modified and deactivated codes. CR 14492 loads the July 1, 2026 lists with an effective date of October 1, 2026 and an implementation date of October 5, 2026.

Why do deactivated codes still show up on some remittances?

CMS allows deactivated CARCs and RARCs in derivative messages in two cases: coordination of benefits claims where Medicare is secondary and the primary payer's adjudication date predates the deactivation, and reversal and correction claims forwarded before the deactivation date. A worklist rule keyed to a deactivated code should route to review, not silently drop the line.

How does Work Genie assign a denial to an owner?

Every 835 posts line by line. Each adjustment is read against a reference master that maps all 297 active CARCs and 1,137 RARCs to a denial category, the category to a root-cause owner such as eligibility, authorization, coding, credentialing or follow-up, and the owner to a deadline derived from the payer's appeal or filing clock. Supervisors allocate the ranked work; every touch is a submitted record that passes a 12-check quality audit with a 24-hour QC service level.

Is there a client result attributable to Work Genie?

Not yet as a stand-alone before-and-after. The spreadsheet-era findings in this paper are diagnostics from client books, and the throughput numbers are internal load tests on synthetic data. The service outcomes on our case-study pages were delivered by our AR team using the platform.

Sources

Checked October 25, 2026. Rules change; confirm against the source before relying on them. Platform figures marked as tests are internal results on synthetic data, not client outcomes.

TechnologyAR Workflow Engine TechnologyDenial Prediction Engine TechnologyRCM Command Center NewsletterThe Work Genie Brief, November 2026 BlogClean claim rate: how to calculate and improve it InsightPayer prior-auth metrics now public Case studyDenial yield prioritization model Case studyTimely filing clock recovery sprint

Want your last 90 days of 835s run through the map?

We resolve every CARC and RARC pair and send back denied dollars by root cause, owner and days to deadline, with the lines that have neither.

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