Denial code lookup

Look up a claim adjustment reason code (CARC) or remittance advice remark code (RARC) from a denial or remittance, and see what it means in plain English, common causes and what billers usually do next.

Denial or remark code

Type a code such as CO 45, co-45, 45, PR 96, A1 or N823. The search runs in your browser.

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What we cover

We list 298 claim adjustment reason codes and 120 remittance advice remark codes, active codes only. The reason code list aims to be complete. The remark code list is a selection of commonly seen codes, not the full list. Every explanation is our own plain-English wording, and the official X12 lists are the authority: X12 Claim Adjustment Reason Codes list and X12 Remittance Advice Remark Codes list. See how we write and check the code pages.

CARC and RARC: what the codes are

When a payer pays a claim for less than you billed, or does not pay it at all, the remittance (the 835 or the paper explanation of payment) says why with codes. A claim adjustment reason code (CARC) gives the main reason for each adjustment. It is a number such as 45 or 97, or a letter and a number such as A1 or B7.

A remittance advice remark code (RARC) adds detail, such as what was missing or which rule applied. Remark codes start with N, M or MA, for example N823 or MA130. They do not stand on their own: read them together with the reason code on the same line.

Group codes: CO, PR, OA and PI

Each reason code on a remittance comes with a group code that says who the adjusted amount belongs to. A search such as "CO 45" is a group code (CO) followed by a reason code (45). The payer picks the group code for each adjustment, so the same reason code can show up as CO 45 on one claim and PR 45 on another. That is why each reason code has a single page here, and the group codes are explained on it.

CO: Contractual Obligation: The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.
PR: Patient Responsibility: The amount is assigned to the patient. Deductibles, coinsurance and copays are the everyday examples. Whether you can collect it still depends on your contract and the patient's plan.
OA: Other Adjustment: Used for adjustments that are neither the provider's contractual write-off nor the patient's share. It often appears with coordination of benefits, for example when another payer already paid.
PI: Payer Initiated Reduction: A reduction the payer made on its own, typically after reviewing the claim, rather than one set by a contract term. The payer does not treat it as the patient's share.

Official group code list: X12 Claim Adjustment Group Codes list.

Commonly searched codes

Codes that people often search for online, based on public search data.

All claim adjustment reason codes (CARC)

Claim adjustment reason codes (298), numeric codes first, then the letter series
Code	What it means	Usually reported as
1	Amount applied to the deductible	PR 1
2	Patient's coinsurance share	PR 2
3	Copayment amount	PR 3
4	Procedure code and modifier do not match	CO 4
5	Code does not fit the place of service	CO 5
6	Code does not fit the patient's age	CO 6
7	Code does not fit the patient's sex	CO 7
8	Code does not fit the provider specialty	CO 8
9	Diagnosis does not fit the patient's age	CO 9
10	Diagnosis does not fit the patient's sex	CO 10
11	Diagnosis does not support the procedure	CO 11
12	Diagnosis does not fit the provider type	CO 12
13	Patient died before the date of service	CO 13
14	Patient born after the date of service	CO 14
16	Missing information or billing error	CO 16
18	Exact duplicate claim or service	OA 18, CO 18
19	Workers' compensation is responsible	OA 19, CO 19
20	Liability insurer is responsible	OA 20, CO 20
21	No-fault insurer is responsible	OA 21, CO 21
22	Another payer may be primary	CO 22, OA 22
23	Prior payer payment affected this claim	OA 23
24	Covered under capitation or managed care	CO 24
26	Service before coverage began	PR 26, CO 26
27	Service after coverage ended	PR 27, CO 27
29	Timely filing limit has passed	CO 29
31	Payer cannot identify the patient	CO 31
32	Patient not an eligible dependent	PR 32, CO 32
33	Subscriber has no dependent coverage	PR 33, CO 33
34	Subscriber has no newborn coverage	PR 34, CO 34
35	Lifetime benefit maximum reached	PR 35
39	Authorization was requested and denied	CO 39, PR 39
40	Did not meet emergency or urgent criteria	CO 40, PR 40
44	Prompt payment discount	CO 44
45	Charge exceeds the allowed amount	CO 45, PR 45
49	Routine or preventive exam not covered	PR 49, CO 49
50	Not medically necessary per the payer	CO 50
51	Pre-existing condition not covered	PR 51, CO 51
53	Care by a relative is not covered	PR 53, CO 53
54	Assistant or extra surgeon not covered	CO 54
55	Experimental or investigational service	CO 55, PR 55
56	Effectiveness not proven per the payer	CO 56, PR 56
58	Wrong or invalid place of service	CO 58
59	Multiple or concurrent procedure rules	CO 59
60	Outpatient care near an inpatient stay	CO 60
61	No second surgical opinion on file	CO 61, PR 61
66	Blood deductible applied	PR 66
69	Day outlier adjustment	CO 69
70	Cost outlier adjustment	CO 70
74	Indirect teaching cost adjustment	CO 74
75	Direct teaching cost adjustment	CO 75
76	Low-income patient load adjustment	CO 76
78	Non-covered days or room charge	CO 78, PR 78
85	Interest owed by the patient	PR 85
89	Professional fees removed from charges	CO 89
90	Drug ingredient cost adjusted	CO 90
91	Dispensing fee adjusted	CO 91
94	Processed above the billed charges	CO 94, OA 94
95	Plan procedures not followed	CO 95, PR 95
96	Service not covered by the plan	CO 96, PR 96
97	Service included in another payment	CO 97
100	Payment sent to the patient	OA 100, PR 100
101	Predetermination estimate	OA 101
102	Adjusted under major medical benefit	CO 102, PR 102
103	Discount the provider offered	CO 103
104	Managed care withhold	CO 104
105	Tax held back from payment	OA 105, CO 105
106	Patient payment option not in effect	PR 106, CO 106
107	Related claim or service not identified	CO 107
108	Rent or purchase rules not met	CO 108
109	Not covered by this payer, send elsewhere	CO 109
110	Billed before the date of service	CO 110
111	Covered only with assignment accepted	CO 111
112	Not furnished directly or not documented	CO 112
114	Not approved by the FDA	CO 114, PR 114
115	Procedure postponed, canceled or delayed	CO 115
116	Advance notice did not meet requirements	CO 116
117	Transport only to the nearest facility	CO 117, PR 117
118	ESRD network support adjustment	CO 118
119	Benefit maximum reached	CO 119, PR 119
121	Indemnification adjustment	CO 121, OA 121
122	Reduced for mental health services	CO 122, PR 122
128	Newborn covered under the mother	CO 128
129	Prior processing looks incorrect	CO 129, OA 129
130	Fee for submitting the claim	CO 130
131	One-time discount for this claim	CO 131
132	Demonstration project adjustment	CO 132
133	Service line still under review	OA 133
134	Technical fees removed from charges	CO 134
135	Interim bill cannot be processed	CO 135
136	Prior payer's coverage rules not followed	OA 136
137	Regulatory surcharge, assessment or tax	CO 137, OA 137
139	Employee funding agreement adjustment	CO 139
140	Patient ID number and name do not match	CO 140
142	Monthly Medicaid patient liability	PR 142
143	Part of the payment is deferred	CO 143, OA 143
144	Incentive adjustment	CO 144, OA 144
146	Diagnosis invalid for the date of service	CO 146
147	Your negotiated rate is missing or expired	CO 147
148	Other provider's information missing	CO 148
149	Lifetime benefit maximum reached	PR 149
150	Records do not support level of service	CO 150
151	Records do not support number or frequency	CO 151
152	Records do not support length of service	CO 152
153	Records do not support dosage	CO 153
154	Records do not support day's supply	CO 154
155	Patient refused the service	CO 155
157	Service resulted from an act of war	CO 157, PR 157
158	Service provided outside the United States	CO 158, PR 158
159	Service resulted from terrorism	CO 159, PR 159
160	Injury from an excluded activity	PR 160, CO 160
161	Bonus for meeting performance goals	CO 161
163	Referenced attachment not received	CO 163
164	Attachment received too late	CO 164
166	Billed after payer's responsibility ended	CO 166
167	Diagnosis not covered	CO 167, PR 167
169	Alternate benefit provided	PR 169, CO 169
170	Denied for this type of provider	CO 170
171	Denied for provider type in this facility	CO 171
172	Adjusted for provider specialty	CO 172
173	Not prescribed by a physician	CO 173
174	Not prescribed before delivery	CO 174
175	Prescription incomplete	CO 175
176	Prescription not current	CO 176
177	Eligibility requirements not met	PR 177, CO 177
178	Spend down not met	PR 178
179	Waiting period not met	PR 179, CO 179
180	Residency requirements not met	PR 180, CO 180
181	Procedure code invalid on date of service	CO 181
182	Modifier invalid on date of service	CO 182
183	Referring provider not eligible to refer	CO 183
184	Ordering provider not eligible	CO 184
185	Rendering provider not eligible	CO 185
186	Level of care change adjustment	CO 186
187	Consumer spending account payment	PR 187
188	Not used per FDA recommendations	CO 188
189	Unlisted code used, specific code exists	CO 189
190	Included in qualified SNF stay payment	CO 190
192	Nonstandard code from a paper remit	OA 192
193	Original decision upheld after review	CO 193, PR 193
194	Anesthesia by the surgeon or attending	CO 194
195	Refund issued to the wrong primary payer	OA 195
197	No prior authorization on file	CO 197
198	Authorization limits exceeded	CO 198
199	Revenue code and procedure code mismatch	CO 199
200	Service during a gap in coverage	PR 200
201	Patient owes under a set-aside agreement	PR 201
202	Personal comfort or convenience item	PR 202, CO 202
203	Service discontinued or reduced	CO 203
204	Not covered under the patient's plan	PR 204, CO 204
205	Pharmacy discount card fee	OA 205, CO 205
206	NPI missing	CO 206
207	NPI in an invalid format	CO 207
208	NPI does not match payer records	CO 208
209	Not collectible from the patient	OA 209
210	Authorization not obtained in time	CO 210
211	NDC not eligible for rebate	CO 211
212	Administrative surcharge not covered	CO 212
213	Self-referral rule violation	CO 213
215	Subrogation from a third-party settlement	OA 215
216	Based on a review organization's findings	CO 216
219	Based on extent of injury	CO 219
222	Over the contract's volume cap	CO 222
223	Mandated adjustment with no specific code	CO 223, OA 223
224	Member identity must be confirmed	CO 224
225	Payer penalty or interest	OA 225
226	Provider did not send requested info	CO 226
227	Patient did not send requested info	PR 227
228	Info not supplied to a previous payer	CO 228, PR 228
229	Medicare left part of a 12X bill aside	PR 229
231	Mutually exclusive procedures	CO 231
232	Institutional transfer amount	CO 232
233	Hospital-acquired condition or error	CO 233
234	Procedure not paid separately	CO 234
235	Sales tax	CO 235, PR 235
236	Procedure combo conflicts same day	CO 236
237	Legislated or regulatory penalty	CO 237
238	Ineligible period reduction (patient)	PR 238
239	Claim spans covered and uncovered dates	CO 239
240	Diagnosis conflicts with birth weight	CO 240
241	Low income subsidy copay	PR 241
242	Not provided by a network or PCP provider	PR 242, CO 242
243	Not authorized by network or PCP provider	CO 243
245	Provider performance program withhold	CO 245
246	Reporting only, not payable	CO 246
247	Facility-billed professional deductible	PR 247
248	Facility-billed professional coinsurance	PR 248
249	Claim flagged as a readmission	CO 249
250	Wrong attachment sent	CO 250
251	Attachment received but incomplete	CO 251
252	Attachment or documentation required	CO 252
253	Sequestration reduction	CO 253
254	Dental plan: bill the medical plan	CO 254, OA 254
256	Not payable under managed care contract	CO 256
257	Exchange grace period: claim pending	OA 257
258	Patient in custody or incarcerated	CO 258, OA 258
259	Extra payment for dental or vision use	CO 259
260	Paid under Medicaid ACA enhanced fees	CO 260
261	Service inconsistent with patient history	CO 261
262	Drug delivery cost adjustment	CO 262
263	Drug shipping cost adjustment	CO 263
264	Drug postage cost adjustment	CO 264
265	Drug administrative cost adjustment	CO 265
266	Drug compounding cost adjustment	CO 266
267	Claim spans more than one month	CO 267
268	Claim crosses into a new year	CO 268
269	Anesthesia not covered for this service	CO 269
270	Medical plan: bill the dental plan	CO 270, OA 270
271	Prior reductions on periodic payment	OA 271
272	Coverage or program guidelines not met	CO 272
273	Coverage or program guidelines exceeded	CO 273, PR 273
274	Not payable under care coordination	CO 274
275	Prior payer's patient share not covered	PR 275
276	Prior payer denied, so not covered here	CO 276, OA 276
277	SHOP grace period: claim pending	OA 277
278	Performance program not met	CO 278, PI 278
279	Out of the member's preferred network	CO 279, PR 279
280	Medical plan: bill the pharmacy plan	CO 280, OA 280
281	Deductible waived by contract	CO 281
282	Code does not fit the type of bill	CO 282
283	Attending provider cannot direct care	CO 283
284	Authorization does not match services	CO 284
285	Appeal procedures not followed	CO 285
286	Appeal filed too late	CO 286
287	Referral limit exceeded	CO 287
288	No referral on file	CO 288
289	Both dental and medical plans exclude it	CO 289, PR 289
290	Dental plan forwarded to medical plan	OA 290, CO 290
291	Medical plan forwarded to dental plan	OA 291, CO 291
292	Medical plan forwarded to pharmacy plan	OA 292, CO 292
293	Payment sent to patient's employer	OA 293
294	Payment sent to an attorney	OA 294
295	Pharmacy DIR adjustment	CO 295
296	Authorization not valid for this provider	CO 296
297	Medical plan: bill the vision plan	CO 297, OA 297
298	Medical plan forwarded to vision plan	OA 298, CO 298
299	Billing provider cannot be paid for this	CO 299
300	Medical plan forwarded to behavioral plan	OA 300, CO 300
301	Medical plan: bill the behavioral plan	CO 301, OA 301
302	Authorization request window has passed	CO 302
303	QMB: prior payer cost sharing not covered	CO 303
304	Medical plan: bill the hearing plan	CO 304, OA 304
305	Medical plan forwarded to hearing plan	OA 305, CO 305
306	Bill type does not match patient status	CO 306
307	Medicare maximum fair price refund	CO 307
308	Funding terms in your contract applied	CO 308
A0	Money going back to the patient	PR A0, OA A0
A1	General denial, see remark code	CO A1, PR A1, OA A1
A5	Medicare PPS capital cost outlier	CO A5, OA A5
A6	Prior stay or 30 day transfer rule not met	CO A6, PR A6
A8	DRG could not be grouped	CO A8
B1	Visits not covered	PR B1, CO B1
B4	Late filing penalty	CO B4
B7	Provider not certified for the service	CO B7
B8	A less costly alternative was available	CO B8, PR B8
B9	Patient is enrolled in hospice	CO B9, OA B9
B10	Reduced: component already paid	CO B10
B11	Sent to the proper payer	OA B11, CO B11
B12	Service not documented in the record	CO B12
B13	Previously paid	OA B13, CO B13
B14	One visit per physician per day	CO B14
B15	Qualifying service not received	CO B15
B16	New patient criteria not met	CO B16
B20	Service furnished by another provider	CO B20
B22	Adjusted based on the diagnosis	CO B22, PR B22
B23	Lab not authorized for this test (CLIA)	CO B23
P1	State rule drove the adjustment	CO P1, OA P1
P2	Not a work related injury or illness	OA P2, CO P2
P3	Workers' comp settled: patient responsible	PR P3
P4	Workers' comp claim found non-compensable	OA P4, CO P4
P5	Paid at payer's usual and customary rate	CO P5, OA P5
P6	Based on entitlement to benefits	OA P6, CO P6
P7	Code not in the fee schedule or database	CO P7
P8	Claim under investigation	OA P8, CO P8
P9	No matching CPT or HCPCS code	CO P9
P10	Payment held at zero during a lawsuit	OA P10, CO P10
P11	On hold for a related lawsuit	OA P11
P12	Workers' comp fee schedule adjustment	CO P12
P13	Reduced under workers' comp rules	CO P13
P14	Included in another same day service	CO P14
P15	Outside workers' comp treatment guidelines	CO P15
P16	Provider not authorized for workers' comp	CO P16, OA P16
P17	Referral not authorized by attending	CO P17
P18	Priced like a similar service	CO P18
P19	Zero relative value in fee schedule	CO P19
P20	Not paid under facility fee schedule	CO P20
P21	Denied under auto PIP or MPC rules	CO P21, OA P21
P22	Adjusted under auto PIP or MPC rules	CO P22, PR P22
P23	Auto PIP or MPC fee schedule adjustment	CO P23
P24	Adjusted under a PPO arrangement	CO P24
P25	Adjusted under a medical provider network	CO P25
P26	Adjusted under a voluntary network (VPN)	CO P26
P27	Denied under auto liability rules	CO P27, OA P27
P28	Adjusted under auto liability rules	CO P28, PR P28
P29	Auto liability fee schedule adjustment	CO P29
P30	Flare up denied: incomplete records	CO P30
P31	Exacerbation denied: time limit exceeded	CO P31
P32	Liability split, partial payment	CO P32, OA P32
Y4	Out-of-network benefits used up	CO Y4, PR Y4

Remittance advice remark codes (RARC)

A selection of commonly seen remark codes, not the full list.

Remittance advice remark codes (120), sorted by code
Code	What it means
M2	Patient was an inpatient at the time
M3	Same or similar equipment already in use
M15	Bundled into another service on the claim
M16	Alert: see payer bulletins or website
M20	Missing or invalid HCPCS code
M25	Documentation does not support the level
M27	Patient not liable for the denied service
M47	Missing or invalid original claim number
M49	Missing or invalid value code or amount
M50	Missing or invalid revenue code
M51	Missing or invalid procedure code
M53	Missing or invalid units or days
M54	Missing or invalid total charges
M56	Missing or invalid payer identifier
M62	Missing or invalid authorization number
M67	Missing or invalid other procedure code
M76	Missing or invalid diagnosis code
M77	Missing or wrong place of service
M79	Missing or invalid line charge
M80	Not payable alongside an earlier service
M81	Code to the highest level of detail
M84	Use code sets in effect for the date
M86	Similar service already paid recently
M114	Priced under a competitive bidding program
M115	Item needs a contract supplier
M119	Missing or invalid NDC
M127	Medical record for the service is missing
M144	Pre and post operative care included
MA01	Alert: how to appeal this decision
MA04	Primary payer information needed
MA07	Alert: claim forwarded to Medicaid
MA08	Alert: bill the other insurer yourself
MA13	Alert: billing limits on patient amounts
MA18	Alert: forwarded to supplemental insurer
MA27	Missing or invalid entitlement ID or name
MA30	Missing or invalid type of bill
MA31	Missing or invalid billing period dates
MA36	Missing or invalid patient name
MA37	Missing or invalid patient address
MA39	Missing or invalid patient sex
MA40	Missing or invalid admission date
MA44	No appeal rights: decision based on law
MA61	Missing or invalid Social Security number
MA63	Missing or invalid principal diagnosis
MA64	Third payer needs both prior payments
MA66	Missing or invalid principal procedure
MA67	Alert: corrects an earlier claim
MA83	Payer order not indicated on claim
MA92	Other insurance plan details missing
MA100	Missing or invalid date of current illness
MA114	Missing or invalid service location
MA120	Missing or invalid CLIA number
MA130	Unprocessable claim: correct and resubmit
MA133	Dates fall inside an inpatient stay
N1	Appeal rights notice
N4	Prior payer EOB missing or invalid
N10	Adjusted after clinical or peer review
N19	Incidental to the main procedure
N20	Not payable with same-day service
N26	Itemized bill missing
N30	Patient not eligible for this service
N31	Prescribing provider ID problem
N34	Wrong claim form or format
N54	Does not match the authorization
N56	Procedure code invalid for service or date
N65	Payer could not price the code
N95	Provider type cannot bill this service
N104	Wrong Medicare contractor
N115	Decision based on an LCD
N117	Once-per-lifetime service
N122	Add-on code billed alone
N130	Check plan benefits for restrictions
N179	Waiting on information from the member
N180	Wrong category for the item billed
N185	Do not resubmit this claim
N192	Patient is Medicaid or QMB
N211	Decision cannot be appealed
N245	Other insurance plan details invalid
N257	Billing provider ID problem
N264	Ordering provider name problem
N265	Ordering provider ID problem
N286	Referring provider ID problem
N290	Rendering provider ID problem
N329	Patient birth date problem
N350	Unlisted code needs a description
N362	Too many days or units
N381	Check your contract terms
N382	Patient ID missing or invalid
N386	Decision based on an NCD
N418	Claim sent to the wrong place
N425	Excluded by law
N432	Recovery audit adjustment
N448	No price loaded for this item
N479	Other payer EOB missing for COB
N517	Submit a new claim with the information
N519	Invalid modifier combination
N522	Crossover copy already on file
N525	Within another service's global period
N569	Not covered for the diagnosis
N570	Credentialing data problem
N574	Ordering provider type not allowed
N575	Ordering provider name mismatch
N640	Frequency limit exceeded
N657	Bill with the right code
N674	Required earlier service not done
N704	No appeal, but can be corrected
N706	Documentation missing
N729	Medical record missing
N767	Provider not enrolled in state Medicaid
N776	Not covered as telehealth
N781	QMB or Medicaid patient: deductible
N808	Provider type excluded for this service
N822	Procedure modifier missing
N823	Procedure modifier invalid or incomplete
N830	Balance billing protections apply
N846	NDC does not match the code
N850	Service narrative missing or invalid
N859	No Surprises Act applied
N864	No Surprises Act emergency rules apply
N892	Delay reason code not accepted

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