Medicare Encounter MAO-001 Duplicates Report – Layout, Example, and Best Practices
September 17, 2025
Medicare Encounter MAO-001: Understanding the Encounter Data Duplicates Report
CMS generates three key reports — MAO-001, MAO-002, and MAO-004 — that provide critical feedback on the outcome of the Encounter Data Processing System (EDPS) editing process. Together, these reports allow Medicare Advantage Organizations (MAOs) to monitor submitted encounter data, identify duplicates, review acceptance/rejection status, and reconcile data with CMS records. In this article, we focus on the MAO-001 Encounter Data Duplicates Report, which specifically identifies duplicate encounters and lines detected by EDPS.
Purpose of the MAO-001 Report
The MAO-001 report is generated only when duplicate errors are detected. It provides detailed information about each duplicate record or line identified during EDPS processing, including the plan's submitted encounter identifiers, the internal EDPS identifiers, and the matching duplicate records found in the Encounter Operational Data Store (EODS). If no duplicates are found, the MAO-001 report is not produced for that submission.
Front-End vs. Back-End Processing
Encounter data files must first clear front-end edits (format validation, submitter ID checks, HIPAA compliance). After passing front-end processing, the files are sent to the EDPS back-end for business rule and duplicate checks. The MAO-001 Encounter Data Duplicates Report is produced only at this back-end stage, when EDPS identifies that one or more encounters or lines are duplicates of records already stored in the Encounter Operational Data Store (EODS).
Encounter Data Submission Workflow
(MAO, Vendor, Clearinghouse)
HIPAA validation, syntax checks
Business & edit checks
-
MAO-001
Encounter Data Duplicates Report
Returned only when duplicates are detected -
MAO-002
Encounter Data Processing Status Report
Record/line-level status, errors, preliminary RA flags
Flow of encounter data from the submitter through CMS front-end and EDPS back-end processing, resulting in MAO-001 (duplicates, when applicable) and MAO-002 (record/line-level status).
Key Components of MAO-001
The MAO-001 report is organized into three record types: Header, Detail, and Trailer. The header identifies the report and file details, the detail section lists duplicate encounters and lines, and the trailer summarizes the number of duplicate lines and total submissions.
The MAO-001 Encounter Data Duplicates Report lists all encounters and service lines that triggered one of the following duplicate edit codes during EDPS back-end processing:
- 98300 – Exact Inpatient Duplicate Encounter
- 98315 – Linked Chart Review Duplicate
- 98320 – Chart Review Duplicate
- 98325 – Service Line(s) Duplicated
Edits 98300, 98315, and 98320 are applied at the header level only, meaning they flag an entire encounter as a duplicate rather than specific service lines.
MAO-001 Report Layout
This table reflects the most recent CMS guidance as of 08/26/2020. If you know of a more recent update or see anything that may be outdated, please reach out so we can keep this resource current.
| Position | Item | Notes | Length | Format |
|---|---|---|---|---|
| Report Layout — MAO-001 Report Header Record | ||||
| 1 | Record Type | 0 = Header | 1 | Numeric, no commas and/or decimals |
| 2 | Delimiter | 1 | Uses the * character value | |
| 3-9 | Report ID | Value is “MAO-001” | 7 | Alphanumeric |
| 10 | Delimiter | 1 | Uses the * character value | |
| 11-18 | Report Date | Date that the report was created by EDPS | 8 | Numeric, format CCYYMDD |
| 19 | Delimiter | 1 | Uses the * character value | |
| 20-27 | Transaction Date | 8 | Numeric, format CCYYMMDD | |
| 28 | Delimiter | 1 | Uses the * character value | |
| 29-67 | Report Description | Value is “Encounter Data Duplicates” | 39 | Alphanumeric, Left Justify, Blank Fill |
| 68 | Delimiter | 1 | Uses the * character value | |
| 69-73 | Filler | 5 | Blank Fill – (Removal of Contract ID) | |
| 74 | Delimiter | 1 | Uses the * character value | |
| 75-104 | Submission Interchange Number | Interchange Sender ID (ISA06) + Interchange Control Number (ISA13) + Interchange Date (ISA09) | 30 | Alphanumeric |
| 105 | Delimiter | 1 | Uses the * character value | |
| 106-108 | Record Type | Value is “INS”, “PRO”, “DME” | 3 | Alphanumeric |
| 109 | Delimiter | 1 | Uses the * character value | |
| 110-113 | Submission File Type | Value is “TEST” or “PROD” | 4 | Alphanumeric |
| 114 | Delimiter | 1 | Uses the * character value | |
| 115-200 | Filler | 86 | Spaces | |
| Report Layout — MAO-001 Report Detail Record | ||||
| 1 | Record Type | 1 = Detail | 1 | Numeric, no commas and/or decimals |
| 2 | Delimiter | 1 | Uses the * character value | |
| 3-9 | Report ID | Value is “MAO-001” | 7 | Alphanumeric |
| 10 | Delimiter | 1 | Uses the * character value | |
| 11-15 | Medicare Advantage | Medicare Contract ID assigned to the MA Plan | 5 | Alphanumeric |
| 16 | Delimiter | 1 | Uses the * character value | |
| 17-36 | Plan Encounter ID (CCN) | Plan Internal Control Number. Loop 2300, element CML01. MAO-generated. | 20 | Alphanumeric |
| 37 | Delimiter | 1 | Uses the * character value | |
| 38-56 | Encounter ICN | Internal Control Number. In encounter data, only 13 spaces represent the ICN; however, additional spaces allow for other use. EDPS-generated. | 19 | Alphanumeric |
| 57 | Delimiter | 1 | Uses the * character value | |
| 58-60 | Encounter Line Number | Internal line number generated by EDPS. For any given ICN (claim document), the line numbers will start from “000” representing the claim level, the first encounter line will start from “001” and increment by 1 for every additional line. | 3 | Numeric, no commas and/or decimals |
| 61 | Delimiter | 1 | Uses the * character value | |
| 62-81 | Duplicate Plan Encounter ID (CCN) | Duplicate Plan Encounter ID stored in Encounter Operational Data Store (EODS). Also known as Duplicate Plan Internal Control Number. MAO-generated | 20 | Alphanumeric |
| 82 | Delimiter | 1 | Uses the * character value | |
| 83-101 | Duplicate Encounter ICN | Duplicate Encounter ICN identified in EODS. In encounter data, only 13 spaces represent the ICN. Additional spaces allow for other use. EDPS-generated | 19 | Alphanumeric |
| 102 | Delimiter | 1 | Uses the * character value | |
| 103-105 | Duplicate Encounter Line Number | Internal line number generated by EDPS | 3 | Numeric, no commas and/or decimals |
| 106 | Delimiter | 1 | Uses the * character value | |
| 107-118 | Medicare Beneficiary Identifier | Beneficiary Health Insurance Encounter Number or Medicare Beneficiary Identifier | 12 | Alpha Number |
| 119 | Delimiter | 1 | Uses the * character value | |
| 120-127 | Date of Service | 8 | Numeric, format CCYYMMDD | |
| 128 | Delimiter | 1 | Uses the * character value | |
| 129-133 | Error Code | Error Code | 5 | Alphanumeric |
| 134 | Delimiter | 1 | Uses the * character value | |
| 135-200 | Filler | 66 | Spaces | |
| Report Layout — MAO-001 Report Trailer Record | ||||
| 1 | Record Type | 9 = Trailer | 1 | Numeric, no commas and/or decimals |
| 2 | Delimiter | 1 | Uses the * character value | |
| 3-9 | Report ID | Value is “MAO-001” | 7 | Alphanumeric |
| 10 | Delimiter | 1 | Uses the * character value | |
| 11-18 | Total Number of Duplicate Encounter Lines Rejected | 8 | Numeric, no commas and/or decimals | |
| 19 | Delimiter | 1 | Uses the * character value | |
| 20-27 | Total Number of Encounter Lines Submitted | 8 | Numeric, no commas and/or decimals | |
| 28 | Delimiter | 1 | Uses the * character value | |
| 29-36 | Total Number of Encounter Records Submitted | 8 | Numeric, no commas and/or decimals | |
| 37 | Delimiter | 1 | Uses the * character value | |
| 38-200 | Filler | 163 | Numeric, no commas and/or decimals | |
Flat-File MAO-001 Example
0*MAO-001*20250912*20250912*Encounter Data Duplicates Report * *SUBMITTERID10004000020250912 *PRO*PROD*
1*MAO-001*H1234*PCCN5552221101 *ICN23456789101 *001*DCCN5552221108 *DICN22445566000 *001*AB45X0234 *20250205*98325*
1*MAO-001*H1234*PCCN5552221102 *ICN23456789102 *001*DCCN5552222208 *DICN22445577000 *001*AB45X0234 *20250208*98325*
1*MAO-001*H1234*PCCN5552221103 *ICN23456789103 *001*DCCN5552223308 *DICN22445588000 *001*AC99X0995 *20250212*98325*
1*MAO-001*H1234*PCCN5552221103 *ICN23456789103 *001*DCCN5552223308 *DICN22445588000 *003*AC99X0995 *20250213*98325*
9*MAO-001*00000004*00000124*00000052*
Report Cadence
The MAO-001 Encounter Data Duplicates Report is generated and returned by EDPS only when duplicates are found. Reports are typically available in the submitter’s SFTP mailbox within five (5) business days of file submission. MAOs should review duplicates promptly to ensure timely corrections or suppression of unnecessary resubmissions.
Best Practices
- Monitor Patterns: Look for recurring duplicate triggers to address systemic issues.
- Automate Retrieval: Download MAO-001 reports as soon as they are posted to your SFTP mailbox.
- Reconcile with Internal Systems: Ensure duplicates are not automatically resubmitted, causing repeat errors.
- Trend Analysis: Track duplicate rates over time to measure process improvements.
Want to dive deeper into reconciliation? Check out Part 1 of this series on the MAO-002 Processing Status Report for line-level acceptance and rejection details.
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