Denial code OA-23 — impact of prior payer(s) adjudication
OA-23 is an other-adjustment code that explains how a prior payer’s payment or adjustments affected this remittance. It is common on secondary claims and is often informational rather than a standalone “denial.”
Last reviewed against published HFMA, CMS, MGMA, Premier, and related primary sources linked on this page on .
What OA-23 means
OA-23 uses group code OA (other adjustment) with reason 23: the line reflects the impact of prior payer(s) adjudication, including payments and/or adjustments. The most common setting is a secondary claim where this payer is coordinating after a primary remittance. First action: reconcile the primary EOB amounts to the secondary remit before changing coding or appealing.
What the code actually says
X12’s short description for reason code 23 is: “The impact of prior payer(s) adjudication including payments and/or adjustments.” (X12 CARC (opens in a new tab), as of this page’s last review). Paired with OA, it is not the same financial story as a CO contractual denial or a PR patient-balance code.
In secondary billing, the secondary payer must know what the primary allowed, paid, and adjusted. OA-23 often appears as the adjustment that accounts for primary activity so the secondary payment math works. It can sit beside patient responsibility or small secondary payments without meaning “appeal me.”
HIPAA remittance standards use these reason codes across Medicare and commercial payers; claims processing context for Medicare is in the Claims Processing Manual (opens in a new tab). COB / MSP background when Medicare is involved is in the MSP manual materials (opens in a new tab).
Most common causes and where they originate
Normal secondary adjudication after primary payment
- Where it originates
- Secondary billing
- How to confirm on the remit
- OA-23 with secondary pay or PR; primary claim cited
- Prevention owner
- Billing ops (reconcile, don’t rework)
Primary allowed/paid amounts sent incorrectly to secondary
- Where it originates
- Secondary claim build
- How to confirm on the remit
- Secondary under/over pays vs contract; mismatch to primary EOB
- Prevention owner
- Billing ops
Primary denial not attached; secondary treats as prior adjudication
- Where it originates
- COB workflow
- How to confirm on the remit
- OA-23 with zero secondary pay; primary was denied
- Prevention owner
- Denial + COB desk
Multiple prior payers (tertiary) stacked incorrectly
- Where it originates
- Billing ops
- How to confirm on the remit
- More than one prior payer loop; residual patient liability odd
- Prevention owner
- Billing ops
Duplicate primary payment reported
- Where it originates
- Payment posting
- How to confirm on the remit
- Secondary adjusts as if primary paid twice
- Prevention owner
- Cash posting
COB order wrong — “secondary” was actually primary
- Where it originates
- Registration
- How to confirm on the remit
- Compare to [CO-22](/denials/co-22) history on the account
- Prevention owner
- Registration
Operational framing for professional and facility secondary claims. Always tie OA-23 back to the primary 835/EOB line by line.
Working the denial, in order
Step 1
Read RARCs and pull the primary remittance
OA-23 without the primary EOB is unworkable. Match procedure lines, modifiers, and dates.
Step 2
Reconcile primary paid + primary adjustments + patient liability
Secondary payment should make sense against remaining liability under the secondary contract. If the math works, post and close.
Step 3
If residual looks wrong, check claim build — not the CPT first
Wrong CAS segments, missing primary paid amount, or wrong claim frequency create secondary noise that looks like a clinical denial.
Step 4
Correct secondary submission or reopen COB order
If primary was never billed correctly, fix primary first ([CO-22](/denials/co-22), [CO-109](/denials/co-109)). Use appeals only when secondary underpaid vs its own policy despite correct primary data ([MLN006562](https://www.cms.gov/files/document/mln006562-medicare-parts-b-appeals-process.pdf) for Medicare ladder overview).
Step 5
Watch each payer’s timely-filing clock
Secondary clocks often run from primary adjudication or from DOS depending on plan — read the manual for that payer.
Before you resubmit
- Primary EOB/835 line matched to the secondary lineSame DOS, codes, and modifiers.
- Primary paid, allowed, and adjustment amounts entered as the secondary requiresPortal vs 837 requirements can differ.
- Patient liability not double-stated across primary and secondaryPosting rules checked before patient statement.
- COB order still correct after primary outcomeA primary denial can change next steps.
- Tertiary coverage considered if residual remainsDo not age secondary AR while a tertiary exists.
- Appeal threshold met for true secondary underpaymentCompare to labour on [cost to collect](/cost-to-collect).
Preventing it upstream
OA-23 “prevention” is mostly clean secondary claim construction and COB master data:
- Standardise primary-EOB capture fields in the billing system.
- Train posters not to reclassify OA-23 as a coding denial.
- SLA the handoff from primary finalisation to secondary drop.
- Fix registration COB so secondaries are not surprises (CO-22).
Management context: denials. Labour: cost to collect.
How this code differs from ones it gets confused with
OA-23 vs [CO-22](/denials/co-22). CO-22 refuses or adjusts because another payer may be primary. OA-23 explains the monetary impact of a prior payer that already adjudicated.
OA-23 vs [CO-45](/denials/co-45). CO-45 is this payer’s contractual write-off to its allowed amount. OA-23 points at prior payer math. Both can appear on one secondary remit — read each CAS segment separately.
OA-23 vs [CO-109](/denials/co-109). Wrong payer/contractor is a routing problem. OA-23 assumes this payer is adjudicating in a coordination context.
If staff treat every OA-23 as an appeal, secondary AR will drown in false work.
Common questions
- What does the OA-23 denial code description actually mean?
- X12 describes reason 23 as the impact of prior payer(s) adjudication, including payments and/or adjustments. With group code OA, it usually explains secondary (or subsequent) coordination math rather than a primary medical-necessity denial.
- Is OA-23 always a denial?
- No. It often appears on paid secondary remittances as an adjustment explanation. Evaluate the whole line: payment, PR, and other CARCs before opening a denial work item.
- Why do I see OA-23 next to patient responsibility?
- After primary payment and contractual adjustments, residual deductible or coinsurance may remain. Secondary may pay part, assign PR, and still show OA-23 for the prior payer impact. Reconcile before billing the patient.
- Should coding change a claim that only has OA-23?
- Not first. Reconcile primary data and COB order. Change coding only if the primary or secondary outcome shows a true coding defect independent of coordination math.
Sources
- X12 Claim Adjustment Reason Codes (CARC) (opens in a new tab) — X12
- CMS Medicare Claims Processing Manual (Pub. 100-04) (opens in a new tab) — Centers for Medicare & Medicaid Services
- CMS Medicare Secondary Payer Manual, Chapter 3 (MSP situations) (opens in a new tab) — Centers for Medicare & Medicaid Services
- CMS MLN006562 — Medicare Parts A & B Appeals Process (opens in a new tab) — Centers for Medicare & Medicaid Services
- Premier: claims adjudication costs providers $25.7 billion (opens in a new tab) — Premier Inc.
Last reviewed against published HFMA, CMS, MGMA, Premier, and related primary sources linked on this page on .
Every benchmark and formula on this page is sourced and dated above. Where a figure is a range, the range is the honest answer, not a hedge. If you think something here is wrong or out of date, tell us — corrections are logged and dated.