CO-173 denial code
Service or equipment was not prescribed by a physician
How to fix it
Obtain the order and resubmit. Orders generally must predate the service.
How to prevent it
Confirm a valid, dated order exists before delivering orderable services or equipment.
In practice
A home health agency bills a visit for a patient whose plan of care was never signed by the ordering physician. The claim returns CO-173: the service was not prescribed by a physician.
Orderable services require an order, and for many benefits that order has to be signed and dated by an eligible practitioner before care begins. An unsigned plan of care is treated as no order at all.
Obtaining the signature and resubmitting works where the order existed and merely lacked a signature. Where no order was ever written, the service is not billable, and reconstructing one afterwards creates a larger problem than the denial.
What sits behind it
The services most affected are those where the billing provider did not make the clinical decision — home health, durable medical equipment, laboratory testing, imaging, therapy. In each, someone else's order authorises the work and the biller depends on it existing.
Signature requirements have hardened over time. Electronic signatures are widely accepted but must be attributable and dated, stamped signatures are generally not accepted, and an order signed long after the service raises questions the reviewer will ask.
The related codes narrow the failure. CO-174 says the order postdated the service, CO-175 that it was incomplete, and CO-176 that it had expired. Reading which arrived tells you whether you are chasing a signature, a date or a whole new order.
Related codes
Terms used here — Medical Necessity · Denial · HIPAA
How we handle it — Denial Management · Claims Management · Medical Billing & Coding
Primary sources
The rules behind CO-173, at the bodies that publish them.
- Evaluation and Management services guide (opens in a new tab)
Centers for Medicare & Medicaid Services — How E/M level is determined under the current medical decision making and time rules. The reference for any dispute about whether documentation supports a level.
- Medicare Claims Processing Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — The operative manual for how Medicare claims must be coded, submitted, adjusted and appealed. When a payer policy and a vendor's advice disagree, this settles it.
- Medicare claims appeals process (opens in a new tab)
Centers for Medicare & Medicaid Services — The five levels of appeal, what each requires and the deadline for each. Missing a level's deadline ends the appeal regardless of the claim's merits.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-173
Where the order genuinely existed and only the signature was outstanding, yes, and resubmission usually succeeds. Where no order was written at all, creating one afterwards misrepresents when the clinical decision was made and is a far more serious problem than the denial.
Generally yes, provided they are attributable to the signer and dated. Stamped signatures are widely rejected, and a signature applied long after the service invites questions about when the clinical decision was actually made.
Those where the billing provider did not make the clinical decision — home health, durable medical equipment, laboratory testing, imaging and therapy among them. In each case the billing provider depends on documentation created by another practice.
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