What does denial code CO-B9 mean?

The patient is enrolled in a Medicare hospice benefit, so the claim as submitted routes to the wrong payer. Rebill with GV (attending, terminal illness) or GW (unrelated care), or bill the hospice for plan-of-care services.

What is the difference between the GV and GW modifiers?

GV marks the designated attending physician treating the terminal illness; GW marks services unrelated to the terminal condition.

CO-B9 Denial Code: Patient Enrolled in Hospice — GV/GW Fixes

Q: Can I bill the patient after a CO-B9 denial?

No - CO is a contractual obligation code. The fix is routing: rebill with the right hospice modifier or invoice the hospice.

What Does CO-B9 Mean?

Code B9''s text: "Patient is enrolled in a Hospice." The moment a Medicare patient elects the hospice benefit, payment rules change for every provider who touches them — services related to the terminal illness route through the hospice's bundled per-diem, and ordinary Part B claims start bouncing with CO-B9. The claim is not wrong because the care was wrong; it is wrong because it ignored a benefit election your practice, in most real cases, simply never heard about from anyone. The good news: most B9 denials are recoverable once you know which of three paths the encounter belongs to.

The three-question triage: (1) Was the service related to the terminal illness? (2) Is your physician the patient's designated attending? (3) Was the service arranged by the hospice? The answers pick the rebill path below.

The Three Rebill Paths

Attending physician, terminal-illness care → rebill with modifier GV. The patient-chosen attending (not employed by the hospice) keeps billing Part B for terminal-condition management — the claim just has to say so. Add GV and resubmit.
Care unrelated to the terminal condition → rebill with modifier GW. The dermatologist treating a rash, the orthopedist setting a wrist — unrelated services stay billable with GW and diagnoses clearly distinct from the terminal illness.
Hospice-arranged or terminal-related care by a non-attending → bill the hospice, not Medicare. Consults and services inside the plan of care are the hospice's financial responsibility under its per-diem. Contact their billing office before writing anything off.

Full background on how hospice elections rewire billing — including where POS 34 applies and the four levels of hospice care — lives in our POS 34 guide.

Why It Keeps Happening

Elections happen between visits: a patient hospitalized last month elected hospice at discharge; your schedule still says "routine follow-up"
Eligibility checks that skip the hospice flag: Medicare eligibility responses carry hospice election data — but only help if someone reads that segment
Election/revocation timing: patients revoke and re-elect; claims spanning a boundary need splitting by date range
Missing GV/GW habits: practices that treat hospice patients regularly but leave modifier logic to memory instead of charge-entry rules

Prevention

Make the hospice flag part of every Medicare eligibility verification — it is in the response data already; surface it in your front-desk workflow
Flag hospice-enrolled patients in the PM system so charge entry prompts for GV or GW before the claim leaves
Train schedulers to ask one question when family calls for an elderly patient: "has anything changed with their care team recently?" — hospice elections surface in that answer constantly
Track B9 denials by patient month over month — a repeat offender on the report means the hospice flag never actually made it into the chart workflow

A Worked Example: One Patient, Three Claims

A cardiology practice has followed a heart-failure patient for years. In June, the patient — also fighting metastatic cancer — elects hospice; nobody tells cardiology. July's claims tell the story: Claim 1, a routine heart-failure follow-up, denies CO-B9. The cardiologist is not the designated attending (the oncologist is), and heart failure management in this patient is intertwined with the terminal picture — this one belongs to the hospice conversation, not Medicare. Claim 2, a pacemaker check for a device issue genuinely independent of the terminal illness, rebills with GW and pays. Claim 3 — the oncologist's own visit — rebills with GV as the attending and pays. Three identical-looking B9 denials, three different correct answers, all decided by the same triage questions. The practice that works them as one generic denial writes off two payable claims; the practice that triages recovers both and routes the third correctly. That is the entire skill of CO-B9 in one patient: same code on the remit, three different destinations for the money, and the triage questions doing all of the deciding.

Frequently Asked Questions

Can I bill the patient after a CO-B9 denial?

No — CO is a contractual obligation code, and the fix is routing, not patient billing. Rebill with GV/GW as the facts support, or bill the hospice for plan-of-care services.

How do I find out if a patient elected hospice?

Medicare eligibility responses include hospice election periods and the hospice provider. Check it at every visit for Medicare patients — elections happen between appointments.

What is the difference between GV and GW?

GV = you are the designated attending physician treating the terminal illness. GW = the service is unrelated to the terminal condition. One of them belongs on nearly every Part B claim for a hospice-enrolled patient.

The service was hospice-related but we are not the attending — is it lost?

Not necessarily. If the hospice arranged or benefited from the service, it belongs on their per-diem — invoice the hospice directly. Money is only lost when nobody routes the claim anywhere.

CO-B9 Denial Code: Patient Enrolled in Hospice