🚀 Live & improving daily! New courses, features, and content added every day.
DenialPro
HomeDenial Code HubCO-288
CO-288CO CodeAuthorizationFrequency: High Last Reviewed August 2026 Source: X12 / WPC

CO-288 Denial Code — Referral Absent

CO-288 means the payer required a referral for the service billed, but no referral was on file or included with the claim. This is a contractual adjustment — the provider must obtain the referral and resubmit as a corrected claim. It is most common in HMO, POS, and managed Medicaid plans where the primary care provider (PCP) must authorize specialist visits.

Resolution Steps Appeal GuidanceFAQ

Quick Answer

CO-288 means a referral was required but absent. Verify whether a referral was obtained from the PCP, request one retroactively if possible, and resubmit as a corrected claim (frequency type 7) with the referral attached. If the plan does not allow retroactive referrals, appeal with documentation showing the service was medically necessary.

Official Definition

Referral absent.

Code Type
CO — Contractual Obligation
Category
Authorization
Impact Level
Medium

What This Code Means

CO-288 means the payer required a referral for the service billed, but no referral was on file or included with the claim. This is a contractual adjustment — the provider must obtain the referral and resubmit as a corrected claim. It is most common in HMO, POS, and managed Medicaid plans where the primary care provider (PCP) must authorize specialist visits.

Status

Review Authorization

Recommended Action

1Review the denial message.
2Verify whether authorization was obtained.
3Check authorization number and validity.
4Contact the payer if authorization was denied.
5Appeal with authorization documentation if appropriate.

Same standard code · different claim context

How CO-288 can be investigated across specialties

CARCs and RARCs are not separate code sets for radiology, gastro, hospital, or professional billing. The code meaning stays standardized; the claim fields, documentation, payer rules, and next checks change by setting.

Professional / Office

Check CMS-1500/837P fields, rendering/billing NPI, diagnosis, modifier, place of service, authorization, and payer policy.

Hospital / Facility

Check UB-04/837I bill type, revenue code, status, inpatient/outpatient rules, authorization, and line-level ERA detail.

Radiology

Check 26/TC component billing, imaging authorization, medical necessity, site of service, same-day edits, and referring provider data.

Gastroenterology

Check procedure relationships, screening vs diagnostic context, modifiers, pathology/anesthesia relationships, authorization, and payer edits.

Behavioral Health

Check provider credential, behavioral-health carve-out, authorization, units/time, telehealth, place of service, and plan-specific rules.

Therapy / Rehab

Check therapy modifiers, timed units, benefit limits, authorization, plan of care/documentation, and NCCI/payer edits.

DME / Supplies

Check HCPCS, modifiers, same/similar equipment, medical necessity, proof of delivery, authorization, and supplier enrollment.

Lab / Pathology

Check CLIA, ordering/referring data, diagnosis support, frequency, panel bundling, specimen/documentation, and payer medical policy.

Financial Impact

Avg. Denial Rate
3-7% of specialist claims in HMO/POS plans
Days to Resolve
10–30 days (depends on retro-referral turnaround)
Appeal Success Rate
60-70% when retroactive referral is obtained or medical necessity is documented
Revenue Risk
Medium — can become permanent loss if the plan does not allow retroactive referrals

Should This Go to Coding?

USUALLY NOT CODING

Do not send every denial to Coding. Coding is appropriate only when the resolution requires coding judgment rather than an administrative or payer follow-up action.

Send to Coding When

A CPT/HCPCS, ICD-10, modifier, NCCI edit, code pair, sequencing rule, or documentation-to-code decision must be reviewed.

Do Not Send to Coding When

Eligibility or member ID issue.
COB or wrong payer.
Missing authorization with no coding question.
Timely filing.
Contractual adjustment such as validated CO-45.
Deductible, coinsurance, or copay after secondary coverage is checked.

Simple rule: If you would have to choose, change, or defend a CPT/HCPCS, ICD-10, modifier, code pair, NCCI edit, or documentation-to-code decision, Coding should review it.

Corrected Claim, Reconsideration, Appeal, or Something Else?

RESEARCH FIRST

Use the ERA/EOB, RARC, payer portal, policy, claim history, and internal workflow to decide between corrected claim, reconsideration, appeal, coding review, payer follow-up, patient responsibility, or adjustment.

Corrected claim: use when your original claim data was wrong or incomplete.
Reconsideration: use when the claim was processed but the payer should review it again, often with added information.
Appeal: use when you disagree with the payer decision and have evidence supporting payment.
Do not duplicate: do not send multiple paths at once unless the payer specifically instructs you to.
See payer-specific submission methods

Should I Adjust This Balance?

DO NOT ADJUST YET

Treat the balance as recoverable until research shows otherwise. The goal of insurance collections is to resolve the denial and obtain payment when a valid recovery path exists.

Read the full ERA/EOB, including all CARC and RARC codes.
Review payer portal status, claim history, and prior notes.
Check eligibility, COB, coding, authorization, medical necessity, and payer policy as relevant.
Choose the correct action: corrected claim, reconsideration, appeal, coding review, payer follow-up, patient responsibility, or adjustment.
Adjust only when the reason is confirmed, the claim is not recoverable, and your organization authorizes the adjustment.

Collections rule: A denial code by itself does not automatically mean write-off. Work the claim for payment first when a valid recovery path exists.

What Should My Account Note Say?

4-Part Note Formula

WHAT HAPPENED + WHAT YOU REVIEWED/DID + WHY THAT ACTION WAS CORRECT + WHAT HAPPENS NEXT

General Denial Note

REVIEWED ERA/EOB FOR CO-288. PAYER PROCESSED/DENIED $[AMOUNT] DUE TO [DENIAL REASON + CARC/RARC]. VERIFIED [PORTAL/ELIGIBILITY/CLAIM HISTORY/POLICY/CODING/AUTHORIZATION]. [ACTION TAKEN] BECAUSE [WHY THIS ACTION IS SUPPORTED]. REMAINING BALANCE $[BALANCE]. WILL FOLLOW UP IN [TIMEFRAME] OR NO FURTHER PAYER ACTION REQUIRED.

Adjustment Note

REVIEWED ERA/EOB FOR CO-288. PAYER APPLIED $[AMOUNT] AS [CONTRACTUAL/NONPAYABLE REASON]. VERIFIED FINAL ADJUDICATION, [CONTRACT/POLICY/CODING REVIEW], AND NO ADDITIONAL RECOVERY PATH. ADJUSTED/REQUESTED ADJUSTMENT OF $[AMOUNT] PER ORGANIZATIONAL WORKFLOW. REMAINING BALANCE $[BALANCE]. [FOLLOW-UP OR RESOLVED].

Current decision: DO NOT ADJUST YET. Do not document an action you did not actually perform. Do not say a payment was posted unless you personally posted it.

How to Investigate

Investigation Checklist

Step-by-Step Workflow

1Verify the patient plan type — HMO, POS, and managed Medicaid typically require referrals
2Check the payer portal for any existing referral on file for this patient and DOS
3Contact the PCP office to confirm whether a referral was generated
4Verify the referral covers the correct specialist, service, and date range
5Determine whether the plan allows retroactive referrals
6If the referral exists but was not submitted: obtain a copy for resubmission

Common Causes

1
Specialist visit billed without a PCP referral on HMO or POS plan
2
Referral was obtained but not submitted with the claim
3
Referral expired before the date of service
4
Referral was for a different specialist or service than billed
5
Patient visited an out-of-network specialist without referral
6
Managed Medicaid plan requiring PCP gatekeeper authorization

Related Denial Codes

CO-197CO-198N489CO-15CO-31

Step-by-Step Resolution

If a referral exists: attach it and resubmit as a corrected claim (frequency type 7)
If no referral exists and the plan allows retroactive: request one from the PCP immediately
If the plan does not allow retroactive referrals: appeal with medical necessity documentation
If the referral was for a different service: obtain a corrected referral and resubmit
If the patient went out of network without referral: may need to write off or bill patient per plan rules

Appeal Guidance

Appeal Grounds

The service was medically necessary and a referral was obtained but not properly transmitted, or the plan should allow a retroactive referral given the clinical urgency.

Appeal Letter Template

We are appealing the CO-288 denial for [patient], DOS [date], claim [ID]. The service was medically necessary as documented in the attached records. [A referral was obtained on [date] but not transmitted with the original claim / A retroactive referral has been requested from the PCP]. We respectfully request reconsideration and payment.

Required Documentation Checklist

Medical records showing medical necessity
PCP referral if it exists
Proof of referral request if retroactive
Clinical notes showing urgency if applicable

Real-World Examples

Referral Not Submitted

Won
Situation

A specialist visit was referred by the PCP but the referral was not attached to the claim. CO-288 returned on an HMO plan.

Outcome

Obtained the referral from the PCP office, attached it, and resubmitted as a corrected claim (type 7). Paid on next cycle.

Expired Referral

Won
Situation

The PCP referral had expired 3 days before the specialist visit. CO-288 returned.

Outcome

Requested a retroactive referral from the PCP citing clinical necessity. PCP issued a new referral covering the DOS. Resubmitted and paid.

Patient Responsibility

Can you bill the patient?
No
When
Not billable — CO-288 is a contractual denial. Do not bill the patient.

Never bill a patient for a CO-288. The referral requirement is a plan rule, not a patient financial responsibility.

Frequently Asked Questions About CO-288

Educational Platform Notice

DenialPro is an educational platform designed to teach medical billing denial management.

Do not submit Protected Health Information (PHI), personally identifiable information (PII), patient names, member IDs, claim numbers, dates of birth, medical record numbers, or confidential healthcare information.

Always verify guidance with official payer policies, CMS guidance, coding guidelines, and applicable regulations.

Need More Help?

Take the next step toward mastering denial management.

Learn in DenialPro Academy

Interactive courses with quizzes, practice labs, real-world scenarios, and certification.

Browse Courses

Practice This Denial

Code lookup is free. Hands on account labs, graded practice, and simulators are premium.

Open Practice Center

Get DenialPro Services

Expert denial management consulting and done-for-you appeal services.

Explore Services