CO-303: Prior Payer Patient Responsibility Not Covered for QMB
Accept the adjustment for confirmed QMB patients. Appeal only if the QMB status determination is incorrect.
What Does CO-303 Mean?
The provider's contractual obligation requires absorbing the Medicare cost-sharing amount for QMB patients. This is a legal requirement, not a negotiable adjustment.
CARC 303 applies to Qualified Medicare Beneficiaries (QMB) — dual-eligible individuals who have both Medicare and Medicaid coverage. Under federal law, providers are prohibited from billing QMB patients for Medicare cost-sharing amounts such as deductibles, coinsurance, and copayments. When Medicaid (or the state program) does not cover these cost-sharing amounts, the provider must absorb them.
This code appears when the provider attempted to collect or bill the patient's Medicare cost-sharing, or when the coordination between Medicare and Medicaid results in the cost-sharing amount being written off. The provider cannot balance-bill the patient for this amount regardless of whether the state Medicaid program pays the cost-sharing.
Common Causes
| Cause | Frequency |
|---|---|
| QMB beneficiary balance billing Provider attempted to collect Medicare cost-sharing (deductible, coinsurance, copayment) from a Qualified Medicare Beneficiary, which is prohibited under federal law | Most Common |
| Medicaid not covering Medicare cost-sharing State Medicaid program does not cover the prior payer's patient responsibility for the QMB beneficiary | Most Common |
| Incorrect patient eligibility verification Provider did not verify QMB status during eligibility check, leading to improper billing of patient responsibility | Common |
| Coordination of benefits error Incorrect processing between Medicare and Medicaid resulted in improper assignment of patient responsibility | Common |
How to Resolve
- Verify the patient's QMB eligibility status through your state Medicaid portal
- Accept the adjustment and do not attempt to collect from the QMB patient — this is prohibited by federal law
- If the patient is not QMB, verify eligibility and appeal with documentation showing the patient's actual status
- Review your state's Medicaid policies on QMB cost-sharing coverage
- Adjust your billing system to flag QMB patients to prevent future improper billing
Appeal only if the patient's QMB status is incorrect. Provide documentation showing the patient is not a Qualified Medicare Beneficiary, including eligibility verification records. If the patient is QMB, the cost-sharing must be written off per federal law.
Common RARC Pairings
The RARC code tells you exactly what triggered the CO-303:
| RARC | Description |
|---|---|
| N381 | Alert: Consult your contractual agreement for restrictions, billing, and payment information. Review QMB billing restrictions — providers cannot balance-bill QMB patients for Medicare cost-sharing → |
| N130 | Alert: You may need to review plan documents or guidelines. Review state Medicaid guidelines for QMB cost-sharing coverage → |
How to Prevent CO-303
- Verify QMB eligibility for all Medicare patients during registration using your state Medicaid verification system
- Train front-desk staff to identify dual-eligible and QMB patients
- Configure billing systems to automatically flag QMB patients and suppress cost-sharing billing
- Stay current with federal and state regulations regarding QMB billing restrictions
- Implement automated eligibility verification that checks both Medicare and Medicaid status
Also Filed As
The same CARC 303 may appear with different Group Codes:
Related Denial Codes
Sources
- https://x12.org/codes/claim-adjustment-reason-codes
- https://www.mdclarity.com/denial-code/303
- https://www.cms.gov/medicare-medicaid-coordination/medicare-and-medicaid-coordination/medicare-medicaid-coordination-office
- Codes maintained by X12. Visit x12.org for official definitions.