CO-173: Service/Equipment Not Prescribed by Physician
No physician prescription on file. This is a provider write-off. Obtain the order and resubmit, or write off the amount if no order can be secured.
What Does CO-173 Mean?
CO-173 indicates a contractual write-off because the provider delivered a service or equipment without a documented physician prescription. This is a provider-side compliance failure, and the adjustment cannot be transferred to the patient. The provider is responsible for ensuring all orders are properly documented before rendering services and submitting claims.
When CARC 173 appears on a remittance, the payer is telling you that the service or piece of equipment you billed was not backed by a physician prescription or order. Payers require a valid physician order as a prerequisite for reimbursement on many service types — particularly durable medical equipment, home health services, clinical lab tests, and certain therapies. Without that documented order, the payer treats the service as unauthorized and denies the claim.
This code almost always appears with Group Code CO, placing the financial burden on the provider. The denial signals a documentation compliance failure: either the physician order was never obtained, it was incomplete, or it was not included with the claim submission. In some cases, the order exists in the patient's medical record but was not properly communicated to the billing department or was not attached to the claim.
Co-173 is distinct from CARC 174 (service not prescribed prior to delivery), which focuses on timing. CARC 173 is broader — the payer found no prescription at all, regardless of timing. Resolution typically involves locating or obtaining the physician order and resubmitting, though if the service was truly delivered without a prescription, the provider may need to absorb the cost.
Common Causes
| Cause | Frequency |
|---|---|
| Missing physician order or prescription The service or equipment was provided without a valid physician prescription or order on file, which is required by the payer before the service can be reimbursed | Most Common |
| Incomplete or illegible prescription documentation The prescription exists but is missing essential elements such as diagnosis codes, physician signature, date, or specific medical necessity language required by the payer | Most Common |
| Non-physician ordering provider The order was written by a non-physician provider (e.g., NP, PA) when the payer requires a physician signature for the specific service or equipment type | Common |
| Service not meeting coverage criteria The payer deems the service experimental, investigational, or not meeting specific coverage guidelines, effectively treating it as not properly prescribed | Common |
| Missing prior authorization The service or equipment required prior authorization that was not obtained before delivery, and the payer considers this equivalent to not being prescribed | Common |
| Coding errors linking wrong service to order Incorrect procedure or diagnosis codes caused the claim to appear as though the service was not associated with a valid physician order | Occasional |
How to Resolve
Locate or obtain the missing physician prescription, then resubmit the claim with complete documentation.
- Locate the physician order Search the patient's medical record, EHR order entries, and faxed referrals for evidence of a physician prescription. Check whether the order was created but not linked to the claim.
- Request physician documentation Contact the ordering physician to obtain a signed order with all required elements. If the physician did verbally order the service, request they formalize it in writing with their signature.
- Resubmit or appeal Attach the physician order and supporting medical records to a corrected claim or appeal. Clearly reference the original claim number and explain that the prescription documentation was omitted from the initial submission.
Common RARC Pairings
The RARC code tells you exactly what triggered the CO-173:
| RARC | Description |
|---|---|
| N362 | The provider must obtain a signed physician order/prescription prior to dispensing/providing the service or item. |
| MA130 | Your claim contains incomplete and/or invalid information, and no appeal rights are afforded. |
| N56 | Procedure code billed is not correct/valid for the services billed or the date of service billed. |
How to Prevent CO-173
- Implement a pre-service verification step that confirms a signed physician order exists before scheduling or delivering any service that requires one
- Use EHR order entry systems with required fields that prevent incomplete orders from being saved
- Establish a billing department checklist that verifies prescription documentation is attached to every claim before submission
- Train clinical staff on which service types require a physician prescription versus those that do not
General Prevention
- Ensure all services and equipment have a valid, signed physician prescription or order on file before delivery
- Implement pre-authorization workflows that verify prescription requirements are met before rendering services
- Train staff on documentation requirements including what constitutes a complete prescription for each service type
- Use electronic health record systems with required-field prompts to prevent incomplete orders from proceeding
- Conduct regular audits of prescription documentation to identify and correct gaps before claim submission
- Stay current on payer-specific policies regarding which providers are authorized to prescribe specific services or equipment
- Establish communication protocols between clinical and billing departments to flag orders that lack required documentation
Also Filed As
The same CARC 173 may appear with different Group Codes:
Related Denial Codes
Sources
- https://www.mdclarity.com/denial-code/173
- https://x12.org/codes/claim-adjustment-reason-codes
- Codes maintained by X12. Visit x12.org for official definitions.