MA13 remark code

Remittance advice remark code MA13. Remark codes add detail to the reason code on the same claim line.

Alert: billing limits on patient amounts

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 MA13 means

An informational alert that billing the patient for amounts not shown as patient responsibility can lead to penalties.

This remark reminds the provider that only amounts reported under the patient responsibility group code should be collected from the patient. Billing the patient for other adjusted amounts can bring penalties.

It is an alert, not a reason for nonpayment. It often appears where a contractual adjustment has been taken.

Common causes

• The claim includes contractual or other adjustments that are not patient responsibility.
• The payer adds this reminder to remittances where balance billing is restricted.
• A line was adjusted under group code CO.

What to do next

1. Check which amounts on the remittance are under group code PR before sending a statement.
2. Post CO adjustments according to your contract rather than moving them to the patient.
3. Refund the patient if a statement already collected an amount that was not patient responsibility.

Related codes

• 45 (reason code) Charge exceeds the allowed amount
• N830 (remark code) Balance billing protections apply