Medicare Part B Denial Codes for SNF Supply Claims: CARC and RARC Guide

Every denied Part B supply claim on your 835 remittance carries at least one CARC, usually paired with a RARC. Together they are a diagnostic readout: what went wrong, whether it can be appealed, and in most cases what to do next. Read that way, a denial file is workable rather than a write-off bucket.

What CARC and RARC Codes Are

CARC stands for Claim Adjustment Reason Code. It is the primary explanation for why a claim was denied or reduced, and every adjusted Medicare claim gets at least one. RARC stands for Remittance Advice Remark Code and supplements the CARC. If the CARC is the chapter, the RARC is the paragraph that names the specific cause or the next step.

The CARC list is maintained by X12 and the RARC list by CMS, both published as part of the HIPAA 835 transaction standard. Because MACs draw from those standardized lists, the codes read the same regardless of region. Read them together: a CARC 50 with RARC N115 tells you something a CARC 50 alone does not.

Why SNF Part B Supply Denials Follow Their Own Patterns

Two structural realities drive most of the denial exposure in this setting. The first is consolidated billing. Under the Balanced Budget Act of 1997, codified at 42 CFR 411.15(p), the SNF is responsible for most services furnished to residents in a covered Part A stay, including most supply categories. A Part B claim for those supplies during a covered stay is denied.

The second is documentation. Part B coverage for supplies requires a Standard Written Order, supporting clinical documentation, and a valid ICD-10 diagnosis that maps to the coverage criteria that apply to the item. Break a link in that chain and the claim comes back denied.

The CARC Codes That Appear Most Often

CARC 97: Bundled into another service

The item is included in payment for another service already adjudicated. In a SNF, this commonly points to a resident in a covered Part A stay when the Part B claim was submitted. Pull the resident's Part A benefit period dates and compare them to the dates of service. Where the item is on the consolidated billing exclusion list, or the stay was not covered, the analysis is different, so check the stay dates before writing the claim off. Where consolidated billing genuinely applies, the fix is upstream: flag Part A status before a Part B claim generates. Paired with RARC M2 ("not paid separately when the patient is an inpatient"), the consolidated billing conflict is confirmed.

CARC 50: Not medically necessary

The MAC concluded the item does not meet coverage criteria for the diagnosis, quantity, or frequency billed. Pull the Standard Written Order, the clinical notes, and the ICD-10 codes, and compare them against the coverage criteria that apply. Often fixable with documentation: file a redetermination with the SWO, physician notes, and a written rationale. Do not simply resubmit, which flags as a duplicate. Paired with RARC N115, the decision was based on a Local Coverage Determination, and that LCD is the appeal roadmap.

CARC 4: Modifier inconsistent or missing

A coding error rather than a coverage question. Verify the HCPCS and modifier combination against the applicable fee schedule and coverage policy, correct it, and resubmit.

CARC 96: Non-covered charges

The item is not covered for this patient or in this setting. Verify the code first, since some of these denials trace to the wrong HCPCS code for the item furnished. One example specific to this model: under traditional Medicare, enteral nutrition runs through the DME MAC pathway under the prosthetic device benefit, not the facility's A/B MAC supply claim. Burst bills enteral nutrition for Medicare Advantage residents only.

CARC 16: Missing or invalid information

A required data element is missing or invalid. Look at the RARC first, because CARC 16 alone tells you little. With RARC MA130, the claim is unprocessable and no appeal rights exist: correct the error and resubmit as a new claim. With RARC N519, check the modifier combination. With RARC N432, this is a Recovery Audit adjustment with its own process and timelines.

CARC 29: Timely filing

The claim was submitted after the filing window. Under 42 CFR 424.44, Part B claims must be filed within one calendar year of the date of service, and the exceptions are narrow: administrative error by a government employee, contractor, or agent; retroactive entitlement; retroactive entitlement involving a state Medicaid agency; and retroactive disenrollment from a Medicare Advantage plan or PACE organization. If these denials are trending up, the billing cycle has a lag in it.

CARC 18: Exact duplicate

An identical claim was already submitted and processed. Appealable only where the original processed in error and you can document it.

CARC 119 and CARC 151: Quantity or frequency

CARC 119 means a benefit maximum for the period was reached. CARC 151, more common on supply claims, means the payer deems the information submitted does not support this many services. Check the quantity limits in the applicable coverage policy or fee schedule. Where the quantity was medically necessary and the SWO and physician notes support it, a redetermination with full documentation is worth filing.

The RARC Codes That Change Your Next Move

A MAC does not attach a RARC to every denial, and N115 does not always name the policy in the remittance itself. Not every supply item has an LCD, so where no policy is identified, work from the coverage criteria and the item's HCPCS definition.

When to Appeal and When to Correct

Appeal when the denial is CARC 50 and the documentation meets the coverage criteria, when CARC 119 or 151 hit a claim with clinically supported quantities, and whenever the RARC reads MA01.

Correct and resubmit, rather than appeal, when CARC 16 came from a specific data error or the RARC reads MA130. Fix the upstream process when CARC 97 reflects a genuine consolidated billing conflict, and when CARC 29 shows claims falling outside the filing window.

What Denial Patterns Say About Your Workflow

Sorted and trended over 30 and 90 days, denial codes read as a report card on the billing operation.

• CARC 97 trending up: Part A and Part B status identification at intake is breaking down.
• CARC 50 trending up: the SWO workflow or clinical documentation standard has a gap.
• CARC 16 trending up: claim scrubbing is missing something in modifier logic, NPI entries, or diagnosis structure.
• CARC 29 trending up: claims are sitting too long between service date and submission.

Denial management is part of the billing service at Burst. When we bill Part B supply claims on a contingency basis, we track denials by code, work the appeals worth working, and flag the upstream issues before the next billing cycle. The assessment is free, takes 30 minutes, and ends with written findings.

This article is general information about Medicare billing rules and is not legal or compliance advice. Confirm current requirements with your MAC and your compliance team.