Denial Code Decoder
MA04 — The primary payer's numbers are missing
This claim was submitted as secondary, and the payer cannot adjudicate it because the primary payer's identity or its adjudication amounts are not on it. It is the opposite problem from CO-22: there the payer says someone else should go first, here it accepts that it is second and is asking for what the first one did. Nothing is being denied on the merits, which is why this is not an appeal.
Billable to the patient? No — the claim has not been adjudicated yet, so there is no balance to assign.
Where this denial is born
- Front desk
- Coding
- Claim build
- Submission
- Adjudication
This denial is usually created at the highlighted stage — that is where prevention lives.
Answer the questions — follow the path
The same questions an experienced biller asks, in order. Your answers draw the route to the right action.
Do you have the primary payer's remittance for this claim?
The secondary needs the primary's allowed amount, payment and adjustments — not just proof that a payment happened.
The full decision tree
Do you have the primary payer's remittance for this claim?
The secondary needs the primary's allowed amount, payment and adjustments — not just proof that a payment happened.
- Yes →
Did the secondary claim actually carry those amounts?
Check the coordination-of-benefits data on the transmitted claim, not the screen you typed it into — this is where the two most often differ.
- Yes →
Check the payer's companion guide. If the amounts were sent, this payer may want them in a different loop or segment than your system produces by default. The companion guide is where that is written down.
- No →
Rebuild the secondary with the primary's adjudication. Carry the primary's identity, allowed amount, payment and adjustment amounts, and resubmit. This is completing the claim, not appealing it — no appeal form is involved.
- Yes →
- No →
Get the primary's remittance first. Retrieve it from the payer portal or your posting records. Both payers' filing clocks are running while it is missing, so this is not a task to queue.
Prevention
Post the primary remittance before the secondary claim is built, and let the secondary draw its coordination-of-benefits amounts from the posted adjudication rather than from a manual re-key.
Related reading
The code list, and when it was last checked
X12 maintains the Remittance Advice Remark Codes list, where this code is listed as MA04. A remark code carries no adjustment group of its own — the group you see on the remittance line belongs to the reason code it arrived with. It has been on the list since January 1, 1997.
Checked against the list revision dated July 1, 2026 on August 7, 2026, where it reads as an active code.
Sources
The paragraphs behind the guidance above. A page that tells you what to do about money should show you what the instruction rests on.
- 45 CFR 162.1102 — the adopted standard for the health care claim transaction, the X12 837, which is where a secondary claim carries the primary payer's identity and the amounts it adjudicated (opens in a new tab)
- 42 CFR 489.20(f) and (g) — a provider agreement obliges the provider to maintain a system that identifies primary payers other than Medicare during admission, and to bill those primary payers first (opens in a new tab)
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