Medical Billing Denial Codes and Reasons (2025)

Denials management is the most important work in medical billing because if any claim is not paid and denied from insurance companies due to any reason, it is medical billing company’s responsibility to handle the received medical billing denial codes appropriately and try their best to re-process the claim and receive respective payment.

Claims that do not get paid, come back as denials from insurance carriers with a code mention by insurance companies which is known as denial reason codes. This can be due to posting errors, incorrect procedures, diagnosis codes, lack of information, medical records while filing a claim or missing/incomplete patient details.

Table of Contents

• What are the Main Denial Reasons for the Delay in Processing Claims?
• Top 10 Denial Reason Codes in Medical Billing:
• List of Denial Codes in Medical Billing
• Related Articles:

What are the Main Denial Reasons for the Delay in Processing Claims?

The following reasons for the delay in the process of claims in medical billing. Denials management is a way to collect more revenue from insurance companies.

1. The claim may not have reached the insurance company’s systems. This is possible due to a bombed transmission or due to an error in the clearinghouse or within the insurance company.
2. There could be delay due to backlog in insurance company’s claims processing department. They take longer than usual to process the claims.

Top 10 Denial Reason Codes in Medical Billing:

• [Denial Code CO 27] – The claims will be denied if the patient coverage not effective at the time of Date of service(DOS).

• [CO 22 Denial Code ] – The insurance company may deny the claim stating that their coverage is secondary to the patient.

• [Denial Code CO-31] – The insurance may not be identified as patient records. This could be due to incorrect policy number, incorrect DOB, patient name, etc.

• [CO 29 Denial Code ] – All insurance company has filing limit from DOS. If the claim sent past the limit, it will denied for late filing.

• [CO 96 Denial Code] – Some insurance companies not provided coverage on some specific medical services.

• [Denial Code CO 16] – Sometimes insurance companies required some additional information or records of the patient.

• [Denial Code CO 11] – An insurance company may deny a claim stating that the procedure performed does not match the diagnosis.

• [Denial Code CO 97] – An insurance company may deny a claim stating that services inclusive in another service.

• [Denial Code CO-18] – Some time claim billed twice or thrice to the insurance company so insurance company may deny the claim due to duplicity.

• [Denial Code CO 50] – Denied due to Non-covered services because this is not deemed a ‘medical necessity’ by the payer.

List of Denial Codes in Medical Billing

These codes are also known as ANSI( American National Standard Institutes) Codes

ANSI Codes	Reason
CO-1	Deductible Amount
CO-2	Co-insurance Amount
CO-3	Co-pay Amount
CO-4 denial Code	The CPT or procedure is inconsistent with Modifier
5	The CPT or procedure is inconsistent with the Place of Service.
6	The CPT or procedure is inconsistent with patients’ age
7	The CPT or procedure is inconsistent with patients’ gender.
CO 8 denial code	The CPT or procedure is inconsistent with the providers’ specialty.
CO 9 denial code	The Diagnosis(Dx) code inconsistent patients’ age
10	The Diagnosis(Dx) code inconsistent patients’ gender
CO 11 Denial Code	The Diagnosis(Dx) code inconsistent with CPT or procedure
12	The Diagnosis(Dx) code inconsistent with provider type.
13	The date of death precedes the date of service(DOS)
14	The of birth follows the DOS
15	The authorization number is missing or invalid
CO-16 Denial Code	Claim or service lack information. Required for adjudication.
17	Request information not provided or insufficient.
CO 18	Duplicate claim
19	This work-related injury so its worker’s compensation insurance liability.
20	This injury or illness covered by the liability carrier.
21	This injury or illness is the liability of the No-fault carrier.
CO 22 denial Code	Covered by another payer as per COB info.
CO 23 Denial Code	The impact of prior payer adjudication including payments.
CO 24 denial Code	Charges covered under a Capitation agreement/managed care plan.
25	Payment denied due to stop-loss deductible not met.
26	The expense incurred prior to coverage.
27	The expense incurred coverage terminated.
28	Coverage was not effective at the time service provided.
CO 29 Denial Code	The timely filing limit has been expired.
30	Payment adjusted, patient not met required eligibility like spend down, waiting or residency requirements.
31	The patient cant be identified as our insured.
32	The dependent is not eligible as per records.
33	Subscriber or Insured has no dependent coverage.
34	Subscriber or Insured has no coverage for newborn baby.
35	Lifetime benefit has been reached the maximum.
36	Balance not exceeds the co-payment amount.
37	Balance not exceeds the deductible amount
38	Service not provided by network/primary care provider.
39	Service denied at the time authorization or pre-certification requested.
40	Charges do not qualify for emergency or urgent care.
41	Discount agreed in the preferred provider contract.
42	Charges exceed fee schedule/maximum allowable amount.
43	Gramm Rudman reduction.
44	Prompt pay discount.
CO 45 denial Code	Charges exceed fee schedule/maximum allowable or contracted fee arrangement.
46	The service is not covered.
47	The diagnosis(Dx) is not covered, missing or invalid.
48	The procedure (CPT) is not covered.
49	Routine exam not covered or service is done in conjunction with a routine exam.
CO 50 Denial Code	Service not covered due to not deemed a “Medical Necessity“.
51	A pre-existing condition is not covered.
52	The rendering or referring provider is not eligible for service billed.
53	Services by an immediate relative of the same household are not covered.
54	Multiple physicians or assistants not covered in this case.
55	Procedure or treatment deemed as experimental or investigational by the payer.
56	Procedure or treatment has not been deemed “proven to be effective” by the payer.
57	Payment denied or reduced because payer submitted information does not support.
58	Treatment rendered in an inappropriate or invalid place of service.
59	Claim processed based on multiple/concurrent procedure rules.
60	Outpatient services not covered when performed within a period of time prior to or after inpatient services.
61	Penalty for failure to obtain a second surgical opinion.
62	Payment denied due to the absence of authorization or pre-certification.
63	Correction of the prior claim.
64	Denial revered a per medical review.
65	The procedure code or CPT was incorrect. Payment reflects correct code
66	Blood deductible
67-68	Not Allocated
69	Day outlier amount
70	Adjustment to compensate for an additional cost- Cost outlier
71	Primary payer amount
72	Co-insurance Day
73	Administrative days
74	Indirect medical education adjustment
75	Direct medical education adjustment.
76	Disproportionate share adjustment.
77	Covered days.
78	Non covered days or room charges adjustment.
79	Cost report days
80	Outlier days
81	Discharges
82	PIP days
83	Total Visits
84	Capital Adjustment
85	Patient Interest Adjustment (Use only group code PR)
86	Statutory Adjustment
87	Transfer Amount
88	Adjustment amount/collection against receivable created in prior overpayment.
89	Removed Professional fee from charges
90	Ingredient cost adjustment
91	Dispensing fee adjustment
92	Claim paid in full
93	No claim level adjustment
94	Processed in excess of charges
95	Plan procedure not followed
CO 96 Denial Code	Non-covered charges.
CO 97 Denial Code	Bundeled Services. The payment of this service inclusive in another service.
98	The hospital must file the medicare claim for this inpatient non physician service.
99	Medicare secondary payer adjustment amount.
100	Payment made to patient.
101	Predetermination- anticipated payment upon completeion of service.
102	Major medical adjustment
103	Provider promotional discount
104	Managed care withholding
105	Tax withholding
106	Patient Payment option
107	The related claim or service was not identified on claim.
108	Rent or purchase guidelines were not met.
CO 109 Denial Code	Covered by another payer. Claim must be send to corrected payer.
110	Billing date predates DOS date.
111	Not covered unless provider accept assignment.
112	Service not furnished directly to patient or or not documented.
113	Payment denied as service provided outside USA or as a result of war.
114	Product or procedure not approved by food and drug administration.
115	Procedure postponed cancelled or delayed.
116	The advance notice of indemnification signed by patient not comply with requirement.
117	Transportation is covered only to closest facility that can provide the necessary care.
118	ESRD network support adjustment.
CO 119 Denial Code	Maximum benefit has been reached for this time period or occurance.
120	Patient covered under managed care plan.
121	Indemnification adjustment
122	Psychiatric reduction
123	Overpayment refund by Payer.
124	Payer refund -not our patient
125	submission or billing error
126	Deductible- Major Medical
127	Co-insurance – Major Medical
128	Newborns’ service covered under mothers allowance
CO 129 denial Code	Prior processing information is incorrect.
130	Claim submission fee.
131	Specific negotiated discount on claim
132	Pre arranged demonstration project discount
133	The claim or service is pending for review.
134	Technical fee removed
135	Interim can not be processed
136	Failure to follow prior payers coverage rules.
137	Regulatory surcharge, health related taxes
138	Time limits not met or appeal procedures not followed
139	Subscriber is employed by the provider of services-Contracted funding agreement
140	Patient health identification number and name do not match.
141	Claim spans eligible and ineligible periods of coverage.
142	Monthly Medicaid patient liability amount.
143	Portion of payment deferred
144	Incentive adjustment
145	Premium payment withholding
146	Diagnosis was invalid for DOS reported.
147	Provider contracted rate expired or not on file.
148	Info from another provider was not sufficient or incomplete.
Co 149 Denial Code	Lifetime benefit reached at maximum for this benefit category.
CO 150 Denial Code	Payer submitted info not supported for this service.
CO 151 Denial Code	Payment adjusted as submitted info by payer not supported frequency of service.
152	The information submitted by payer not support this length of service.
153	The information submitted by payer not support this dosage.
154	The information submitted by payer not support this days’ supply.
155	Patient refused the service or procedure.
156	Flexible spending account payment.
157	Service was provided as a result of an act of war.
158	Service was provided outside of USA.
159	Service was provided as a result of terrorism.
160	The injury was the result of an activity which is benefit exclusion.
161	provider performance bonus.
162	State mandate requirement for property & casualty
163	The attachment referenced on the claim was not received.
164	The attachment referenced on the claim was not received within time.
165	Referral absent/exceeded.
166	These services were submitted after the payers responsibility for this plan ended.
167	This diagnosis is not covered.
168	Benefits are not available under this dental plan. Service considered under patient medical plan.
169	Alternative benefit has been provided.
170	Payment denied due to performed by this type of provider.
171	Payment denied due to performed this type of provider. in this type of facility.
172	Payment is adjusted when performed by a provider of this specialty.
173	Service was not prescribed by physician.
174	Service not prescribed prior delivery.
175	Prescription is incomplete.
176	Prescription is not current.
177	Patient not met required eligibility.
178	Patient not met required spend down requirements.
179	Patient not met required waiting requirements.
180	Patient not met required residency requirements.
CO 181 Denial Code	CPT invalid on DOS or not active for Medicare on the DOS.
182	Procedure modifier invalid on DOS
183	The referring provider is not eligible to refer billed service.
184	The prescribing provider is not eligible to prescribe the service billed.
185	The rendering provider is not eligible to perform the service billed.
186	Level of care change adjustment.
187	Health savings account payments.
188	Service or procedure only coverd when used according to FDA recommendations.
189	Not otherwise classified or unlisted procedure code was billed when there is a specific cpt code for service.
190	Payment is included in allowance for skilled nursing facility.
191	Not a work related injury so not liability of workers comp insurance.
192	Non standard adjustment code for paper remittance.
193	Original payment decision is being maintained upon review.
194	Anesthesia performed by assistant or attending surgeon, operating physician.
195	Refund issued to erroneous priority payer for this claim
196	This code is removed.
CO 197 Denial Code	Authorization, pre-certification, notification absent.
198	Authorization, pre-certification, notification exceeded.
199	Procedure code and revenue code do not match.
200	Expense incurred during lapse in coverage.
201	Workers compensation case settled. Patient is responsible through WC medicare set aside arrangement or other agreement.
202	Non covered personal convenience services.
203	Discontinued/reduced services.
CO 204 denial Code	Service, equipment, drug not covered under patient current benefit plan.
205	Pharmacy discount carrd processing fee
206	NPI missing.
207	NPI invalid format.
208	NPI not matched.
209	As per agrerement provider can not collect this amount from patient.
210	Pre-certification, authorization not received timely so payment adjusted.
211	National drug code (NDC) not covered or not eligible.
212	Administrative surcharges not covered.
213	Physician self refferral prohibition legislation non compliance or payer policy.
214	WC claim adjudicated as non compensable.
215	Based on subrogation of a 3rd party settlement.
216	Based on finding of review on organization.
217	Based on payer reasonable and customary fees, no maximum allowable defind by legislated fee arrangement.
218	Based on entitlement to benefit.
219	Based on extent of injury.
220	The applicable fee schedule not contain billed code.
221	Workers Compensation (WC) claim is under review.
222	Exceeds contracted maximum number of days, units, hours by this provider for this period.
223	Adjustment code for mandated federal, state, or local law regulation that is not already covered by another code and is mandated before new code generate or created.
224	Patient identification compromised by identity theft.
225	Penalty or interest payment by payer.
226	Information requested from billing or rendering provider was not provided or insufficient.
227	Information requested from patient or insured provider was not provided or insufficient.
228	Denied to failure of this provider, another provider, or the subscriber to supply requested information to to a previous payer.
229	Partial charge amount not considered by medicare due to initial claim type of bill being 12X.
230	Correlating CPT/HCPCS code is not available to describe this service.
231	Institutional transfer amount- applies to institutional claims only and explains the DRG amount difference when patient care cross multiple institutions.
232	Not available
233	Services related to the treatment of a hospital-acquired condition or preventable medical error.
CO-234 Denial Code	This procedure is not paid separately.
235	Sales tax.
236	The procedure and modifier combination are not compatible with each other.
237	Legislated or regulatory penalty.
CO 252 denial code	A CO-252 denial code means that a claim needs additional documentation or information to support claim.
CO 253 denial code	CO-253 denial code means that the insurance provider has determined that the service or procedure performed is not covered under the patient’s policy, that is why denial of payment.

It is the medical billing and coding company responsibility to manage all denials very effectively and get collect payment from the insurance company. Company’s’ denial management strategy reduces the claim denial ratio and increases the revenue. Denial reason codes list updated by American Medical Association(AMA) from time to time.

Related Articles:

Claim Adjustment Reason Codes | CARC Codes

CPT Codes List

Place of Service Codes (POS)

Revenue Codes List

Taxonomy Codes List