835 Denial Combination

CO-45+MA18

CO

Contractual Obligation · Service-Line Level Adjustment

Contractual Adjustment

What This Combination Means

Note: An informational alert accompanies this denial. The primary payer has reduced the billed charge to their contracted or fee schedule rate, and the provider must write off the difference. Simultaneously, the payer is forwarding claim details to the patient's supplemental insurance, which may cover some or all of the cost-sharing amounts (deductible, coinsurance, copay) but not the contractual write-off itself.

Financial Responsibility

provider writeoff

The provider must absorb the difference between the billed charge and the allowable amount per contract. The supplemental insurer may reimburse patient cost-sharing portions, but the contractual adjustment remains the provider's responsibility.

N/A

Appeal Success

Immediate (write-off)

Avg. Resolution

Easy

Difficulty

No

Appealable

Step-by-Step Resolution

Steps tailored specifically to this CO-45+MA18 combination — not generic advice.

Not Appealable:Contractual fee schedule adjustments are not appealable as they reflect agreed-upon rates between provider and payer.
  1. 1

    Post the contractual adjustment as a write-off in your practice management system

    The CO-45 amount represents the difference between your billed charge and the payer's allowable rate, which must be absorbed per contract

  2. 2

    Verify the allowable amount matches your contracted fee schedule or state/federal rate table

    Confirm the payer applied the correct rate; if discrepancies exist, contact the payer's provider relations to clarify contracted rates

  3. 3

    Monitor for supplemental insurance payment (crossover claim)

    The MA18 alert indicates the primary payer is forwarding claim data to the supplemental insurer; expect secondary payment for patient responsibility portions within typical crossover processing timeframes

Specialty Context

How CO-45+MA18 typically presents across different practice types.

Dental

Common with Medicaid or Medicare Advantage dental plans where billed UCR fees exceed contracted rates; supplemental policies rare in dental but may apply for seniors with Medicare supplement plans covering limited dental benefits

Medical

Routine for Medicare, Medicaid, and commercial insurance claims where billed charges exceed allowable amounts; MA18 frequently seen with Medicare + Medigap or retiree supplemental plans where crossover is automatic

Behavioral Health

Standard for behavioral health providers billing above contracted rates for therapy or psychiatric services; supplemental coverage may include employee assistance programs or secondary behavioral health carve-out plans

Individual Code References

View the standalone definition for each code in this combination.

CARC 45RARC MA18

Medicare Contractor Guidance for CARC 45

Noridian

Payment was made for this claim conditionally because an HHA episode of care has been filed for this patient.

How to Prevent CARC 45 Denials

  • ✓

    Ensure eligibility is verified in the Noridian Medicare Portal for Home Health Episode History (HHEH)

  • ✓

    Utilize the Consolidated Billing Tool on the Noridian Medicare website to inquire on items covered in a HHA episode of care, prior to providing

Noridian Medicare PortalConsolidated Billing ToolFee Schedule

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Synthesized from official definitions — not from training data

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