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Medi-CalTraditional Medicare · Administrative · Claims & Billing · CAHigh impact

Guidance for Medicare/Medi-Cal Crossover Claim Submission on the Paper CMS-1500

Effective date
Jul 21, 2026
Identified
Jul 22, 2026

Summary

California Medi-Cal has issued updated guidance for submitting Medicare/Medi-Cal crossover claims on paper CMS-1500 forms. Providers must now submit crossover claims directly to the California MMIS Fiscal Intermediary at a specific Sacramento address, with strict formatting requirements for key CMS-1500 fields (Boxes 1, 1A, 9A, and 11C) and must attach a corresponding Medicare Remittance Notice with each submission. Claims not meeting these requirements will be returned.

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What to do

Action · 13 steps
01Effective immediately (July 21, 2026): Billing team must implement the following changes.
02Update all CMS-1500 crossover claim submission procedures to route claims to the California MMIS Fiscal Intermediary at P.O.
03Box 15700, Sacramento, CA 95852-1700 instead of any previous addresses;.
04Modify billing system templates and provider instructions to ensure CMS-1500 Box 1 has 'X' marked in BOTH Medicare and Medicaid fields.
05Require Box 1A to contain Medicare ID number.
06Require Box 9A to contain Medi-Cal ID in either 14-digit or 9-digit CIN format.
07Require Box 11C to contain Medicare Carrier Code.
08Update claim submission workflows to mandate a separate copy of the Medicare Remittance Notice (MRN) with every crossover claim.
09Ensure all Medicare-allowed lines from the MRN are included on the crossover claim and match exactly.
10Train billing staff that Medicare-denied lines on the same claim/MRN cannot be paid via crossover.
11Clarify that Medicare Advantage/HMO members require straight Medi-Cal claims with EOB instead of crossover format.
12Failure to comply will result in claim denials and returns.
13Affected providers include all practices billing Medicare/Medi-Cal crossover claims in California.

Original notice

Guidance for Medicare/Medi-Cal Crossover Claim Submission on the Paper CMS-1500
mcweb.apps.prd.cammis.medi-cal.ca.gov · Always check the source before changing claims.
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