CO-59 is Claim Adjustment Reason Code 59 with group code CO. CARC 59 means the line was processed based on multiple or concurrent procedure rules — for example multiple surgery, diagnostic imaging, or concurrent anesthesia. Search demand often uses “co 59 denial code,” so this page targets that phrase. (Primary sources: X12 Claim Adjustment Reason Codes · CMS Medicare Claims Processing Manual, Ch. 12, §40.6 Multiple Surgeries · CMS Ch. 22, §60.1)
Quick answer: Rank the procedures the way the payer (or CMS multiple-surgery rules) ranks them. Confirm modifiers and multiple-procedure indicators. If the secondary line was correctly reduced, post the contractual adjustment. If the wrong line was cut, ranking is wrong, or a modifier should have bypassed the edit, appeal or correct the claim. Check the 835 Healthcare Policy Identification REF when present.
Part of our denial codes library. Written by Manikandan, a revenue cycle management specialist with more than 10 years of US medical billing experience. Last reviewed: 11 October 2026. Official code wording is quoted word for word from X12; Medicare rules link to their CMS or Medicare contractor source.
CO-59 denial code description (official X12 wording)
X12 Claim Adjustment Reason Code 59, verbatim:
“Processed based on multiple or concurrent procedure rules. (For example multiple surgery or diagnostic imaging, concurrent anesthesia.) Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.”
Source: X12 Claim Adjustment Reason Codes, checked 11 October 2026. Start: 01/01/1995 | Last Modified: 07/01/2017.
The CARC is 59. Medicare and many commercial plans report it with group code CO when the reduction is contractual. PR is uncommon but follow the remit.
What CO-59 means in plain English
- CARC 59 means payment was adjusted under multiple-procedure rules. That covers more than one procedure on the same claim. It also covers concurrent anesthesia and some imaging edits.
- It is often a percentage reduction on secondary procedures after ranking. It is not a statement that the service was never performed. Medicare multiple-surgery rules are one common source of that math.
- CO-59 — usually a provider contractual write-off of the reduced portion.
- Always read the policy REF on the 835 when X12 usage says it is present.
CO-59 vs CO-97, CO-234, CO-B15 and CO-45
| Code | Official X12 idea | Difference |
|---|---|---|
| 59 | Processed based on multiple or concurrent procedure rules | Multi-procedure ranking / MPPR-style cut |
| 97 | Benefit included in payment/allowance for another service already adjudicated | Bundled into another paid service |
| 234 | Procedure not paid separately; remark required | Not paid separately — CO-234 |
| B15 | Qualifying other service not received/adjudicated | Dependent service missing |
| 45 | Charge exceeds fee schedule/maximum allowable or contracted amount | Allowed-amount cut — CO-45 |
59 is about multiple-procedure pricing rules. 97/234 are about bundling/packaging. Do not work them identically.
Group code matrix for CARC 59
| Group + 59 | Who carries the amount | Typical next step |
|---|---|---|
| CO-59 | Provider | Verify ranking; write off correct reduction; appeal errors |
| PR-59 | Patient | Rare; confirm before patient bill |
| OA-59 | Neither fits cleanly | Read remarks/REF |
| PI-59 | Payer-initiated | Non-Medicare; investigate |
CMS Ch. 22 §60.1: PR amounts “may be billed to the patient or insured”; CO amounts are generally provider write-offs not billed to the patient.
Remark codes and policy pointers for CARC 59
| Pointer | Role |
|---|---|
| 835 REF (Healthcare Policy Identification) | X12 usage: read this when present for the policy that drove the cut |
| N381 | Contractual agreement alert — N381 |
| M15 | Bundling remark (different problem if present without multi-proc ranking) |
| N20 / plan remarks | Procedure code combinations / multiple procedure messaging when used |
If no remark appears, the CAS*CO*59 amount plus any policy REF is still enough to start ranking review.
Where CO-59 shows up in the 835
SVC*HC:29881*1200.00*1200.00~
SVC*HC:29876*900.00*450.00~
CAS*CO*59*450.00~
- Primary arthroscopy paid in full; secondary procedure reduced under multiple-surgery rules (illustrative only — use the payer’s actual percentage).
- Group CO → contractual write-off of the reduced portion.
Illustrative only — always use the payer’s actual ranking and percentages.
How to fix CO-59: decision path
- List all procedures on the claim/DOS with paid/allowed amounts and modifiers.
- Rank by the payer’s rule (Medicare: multiple surgery indicators and RVU ranking per CMS Ch. 12 §40.6; commercial: contract/MPPR policy).
- Check modifiers (51, 59, XE, XP, XS, XU, 76/77 as applicable) — wrong or missing modifiers cause wrong cuts.
- Confirm the secondary reduction math against the fee schedule.
- If correct — post CO-59 write-off; stop.
- If wrong ranking or wrong line reduced — corrected claim or appeal with operative report, ranking worksheet, and indicator printout.
- If concurrent anesthesia or imaging MPPR — use that specialty’s rules, not surgical flat-rate assumptions.
- Read the policy REF when present and attach it to the ticket.
Medicare and commercial notes
Medicare. CMS explains multiple surgeries in the Medicare Claims Processing Manual, Chapter 12, section 40.6. The rules cover separate procedures by the same physician (or same group) on the same patient and day. Rank the lines with the multiple-surgery indicators. Then apply the manual’s percentage steps to later procedures. Do not hard-code a percentage in your tickets. Check the manual and the remittance. Endoscopic rules can run before standard multiple-surgery logic. Imaging and anesthesia use their own policies. Match the specialty.
Commercial. Many plans mirror MPPR or use contract-specific secondary-procedure percentages. “co 59 denial code” often appears on surgical claims even when staff expected CO-45. Compare the remit math to the contract exhibit.
Not a denial of medical necessity. 59 says the line was priced under multiple-procedure rules, not that the service was non-covered. Keep medical-necessity appeals (CO-50) separate unless a second CARC says so.
Worked example (illustrative)
For example, two ipsilateral knee arthroscopy codes bill on the same DOS. The remit pays the higher RVU line in full. It applies CAS*CO*59 to cut the secondary line under multiple-surgery rules.
Reading it: multiple-surgery pricing; contractual reduction on the secondary.
Fix: confirm Medicare/commercial multiple-surgery indicators allow both codes together, confirm ranking order, confirm modifier 51 (if required by the payer) and any NCCI PTP pairs. If ranking is correct, write off. If the payer ranked a lower-RVU line as primary, appeal with the RVU table and operative report.
Prevention: pre-bill multiple-procedure estimator; coder checklist for same-DOS surgery stacking.
CO-59 appeal or correction template
[Date]
[Payer] Appeals / Provider Service
[Address, fax or portal]
Re: CARC 59 (multiple/concurrent procedure rules) — [appeal / reconsideration]
Patient: [Name] Member ID: [ID] DOB: [MM/DD/YYYY]
Claim number: [Claim #] Date(s) of service: [MM/DD/YYYY]
CPT/HCPCS: [Codes ranked] Group code on remit: [CO / PR]
The remittance shows CAS*[CO/PR]*59. Please reprocess because:
[ ] Incorrect ranking; primary should be [code] per [RVU / contract].
[ ] Modifier [51/59/X{EPSU}] supports separate payment under [policy].
[ ] Multiple-surgery indicator / imaging MPPR rule was misapplied.
[ ] Policy REF [id] does not apply to these codes.
Enclosed: remit, claim, operative report, ranking worksheet, fee schedule,
policy REF / contract excerpt.
[Name, credentials] [Practice, NPI] [Phone / email]
Prevention checklist
- Run same-DOS multi-procedure edits before drop.
- Rank by current RVUs / payer indicators, not charge order.
- Apply modifiers per payer policy (do not add 59 to bypass NCCI without documentation).
- Separate true 59 pricing cuts from 97/234 bundling.
- Post correct CO write-offs without billing patients.
- Keep CMS Ch. 12 §40.6 and imaging/anesthesia MPPR links in the surgery billing SOP.
- Train staff with the CARC & RARC guide.
Related denial codes
- CO-234: procedure not paid separately.
- CO-45: charge exceeds fee schedule/contracted amount.
- CO-151: frequency/units not supported.
- N381: contractual agreement alert.
- CO-50: medical necessity (different issue).
- CARC & RARC guide.
In short
CARC 59 means multiple or concurrent procedure pricing applied. Verify ranking and modifiers, accept correct reductions, appeal mis-ranked lines, and read the policy REF when the 835 includes one.
FAQ
What is the CO-59 denial code description?
X12 describes CARC 59 as “Processed based on multiple or concurrent procedure rules” (for example multiple surgery or diagnostic imaging, concurrent anesthesia), and says to refer to the 835 Healthcare Policy Identification Segment when present. CO-59 is that CARC with group code CO.
Is CO-59 a full denial?
Often no. It usually means a secondary procedure was paid at a reduced percentage under multiple-procedure rules. The service can still be payable — just reduced. Always check the paid/allowed amounts on each line.
How do I fix a CO-59 adjustment?
Rank procedures per payer/CMS rules, verify modifiers and indicators, accept correct math, or appeal/correct when the wrong line was reduced or a bypassing modifier/documentation supports separate payment.
What is the difference between CARC 59 and CARC 97?
59 is multiple/concurrent procedure pricing. 97 means the benefit is included in the payment for another service already adjudicated (bundling). Different appeal packets.
Does Medicare use multiple surgery rules with CARC 59?
Medicare multiple-surgery logic is in CMS Claims Processing Manual Ch. 12 §40.6. Remits may report the reduction with CARC 59 (and/or related payment CARCs). Always match the code on your remittance and the policy REF when present.
Can I bill the patient for CO-59?
Usually no. CO amounts are generally provider write-offs. Bill the patient only when the remit shows PR (or a valid notice shifts liability and patient responsibility is reported). Key named sources on this page include Claim Adjustment Reason Codes, Remittance Advice Remark Codes, the Medicare Claims Processing Manual Chapter 12 multiple surgery section, and Chapter 22 group codes from Centers For Medicare guidance.
Quick facts
| Item | Value |
|---|---|
| X12 code | 59 |
| X12 start | 01/01/1995 |
| Last modified | 07/01/2017 |
| Slug | co-59 |
| Last reviewed | 11 October 2026 |
| Page type | WordPress Page under Denial Codes hub 183 |
| Primary keyword | co 59 denial code |
Quick reference: dates and lists
Claim Adjustment Reason Code 59 started on 01/01/1995. X12 last modified it on 07/01/2017. Medicare Claims Processing Manual Chapter 12 section 40.6 covers Claims for Multiple Surgeries. Diagnostic imaging and concurrent anesthesia use their own multiple-procedure rules. Always read the 835 Healthcare Policy Identification Segment when the remittance prints one.
Sources
- X12, Claim Adjustment Reason Codes (CARC 59, 97, 234, 45, 50). CARC 59 Start 01/01/1995, Last Modified 07/01/2017. Accessed 11 Oct 2026.
- X12, Remittance Advice Remark Codes. Accessed 11 Oct 2026.
- CMS, Medicare Claims Processing Manual (IOM 100-04), Ch. 12, §40.6 Claims for Multiple Surgeries
- CMS, Medicare Claims Processing Manual (IOM 100-04), Ch. 22, §60.1 Group Codes
Access dates and figures on this page were checked on 11 October 2026 against X12 and CMS sources.
Last reviewed: 11 October 2026 · This page is educational and doesn’t replace payer-specific instructions.