OA 305 denial code

Claim adjustment reason code 305. Often reported as OA 305 or CO 305.

Medical plan forwarded to hearing plan

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 305 means

The medical plan found no benefit for the service and forwarded the claim to the patient's hearing plan.

The medical payer decided this is a hearing benefit and passed the claim on for you. If it had not forwarded the claim, code 304 would appear instead.

The decision on payment will come from the hearing plan, so wait for its response before billing anyone else.

Group codes seen with 305

On a remittance, 305 comes after a group code. These are the ones it is most often reported with:

• OA 305 (Other Adjustment): Used for adjustments that are neither the provider's contractual write-off nor the patient's share. It often appears with coordination of benefits, for example when another payer already paid.
• CO 305 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• Hearing aids or related services were billed to the medical plan.
• The payer routes hearing claims to its hearing benefit vendor.
• The service is excluded under medical and covered under hearing.

What to do next

1. Note that the claim was forwarded and to which plan.
2. Track the hearing plan's response and follow up if nothing arrives.
3. Bill the hearing plan directly only if it confirms it did not get the claim.

Related codes

• 304 (reason code) Medical plan: bill the hearing plan