OA 105 denial code

Claim adjustment reason code 105. Often reported as OA 105 or CO 105.

Tax held back from payment

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 105 means

The payer held back part of the payment for taxes as required for that payee.

The payer reduced the payment to withhold tax. This often happens when the payer lacks a valid taxpayer identification or has been directed to apply backup withholding, though rules vary.

The withheld money is usually reported to tax authorities in the provider's name. Your accounting team should know so it is not posted as a write-off.

Group codes seen with 105

On a remittance, 105 comes after a group code. These are the ones it is most often reported with:

• OA 105 (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 105 (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

• The payer has a missing or mismatched taxpayer identification number for the provider.
• The payer was directed to apply backup withholding.
• A state or local tax rule applies to payments made in that area.

What to do next

1. Confirm that the taxpayer identification and legal name on file with the payer are correct.
2. Send updated tax forms to the payer if its records are wrong.
3. Tell your accounting team so the withheld amount is tracked correctly.