Get the full breakdown of the Medicare Monthly Membership Report (MMR), including ARC codes, risk adjustment fields, and payment logic. Ideal for coders and compliance analysts.
Excerpt Introduction:
If you're working in Medicare Advantage or Part D, the MMR is your monthly playbook for payment accuracy. Learn how to decode its 91 fields, understand ARC codes, review RAF logic, and track risk and reimbursement with precision.
📌 What Is the MMR and Why It Matters
The Monthly Membership Report (MMR) is the official CMS data file used to track monthly capitation payments, adjustments, and risk scores for Medicare Advantage and Part D beneficiaries.
Think of it as your financial DNA from CMS — every line item reveals what was paid, why it changed, and what risk model was applied.
Key details:
Format: Fixed-width, 495-character record
Frequency: Monthly
Used in: MA Plans, Part D Plans, Compliance Audits, RAS Submissions
🔍 What’s Inside the MMR? (Overview of the 91 Fields)
The MMR is organized into logical sections. Here’s what you’ll find:
🧍♂️ Beneficiary Demographics
Name, Gender, DOB, State & County Code
Beneficiary ID (includes MBI format)
Hospice, ESRD, Medicaid, Institutional, Dual-Status
📊 Risk Adjustment & Status
RAF A/B (Fields 24–25)
Risk Adjustment Factor Type Code (Field 46)
RAAG – Risk Adjustment Age Group (Field 40)
Low-Income & Medicaid Add-On Fields (Fields 20, 66, 67, 68)
💸 Payments, Premiums & Rebates
Monthly Part A, B, D amounts
Rebate fields (Part C/D)
MTM Add-on, LIS Premium Subsidy, Reinsurance, Direct Subsidy
🔁 Adjustments & Reconciliations
ARC – Adjustment Reason Code (Field 28)
Cleanup ID (Field 91)
Start and End Dates for payment period (Fields 29–30)
🧠 ARC Codes: Why Payments Change (Field 28)
ARC = Adjustment Reason Code, and they’re the "receipt" behind every payment change CMS makes.
Where You'll Find ARC:
MMR Detail Report (Field 28)
MMR Summary Report (Field 4)
PPR/IPPR Capitated Payment Files (Field 4)
🗂️ ARC Categories at a Glance:
Range Reason
00 Standard prospective payments
01–22 Retroactive enrollment & eligibility
23–27 Risk adjustment changes
28–37 Premium/rebate adjustments
38–46 Segment ID or eligibility corrections
50–66 Merge, incarceration, lawful status
90–94 System-driven CMS cleanup events
📘 Notable ARC Codes
01 – Death Notification
07 – Retroactive Hospice
10 – Retroactive Medicaid
25 – Part C RAF Reconciliation
36 – Part D Rate Change
44 – Correction of Previously Failed Payment
65 – Incarceration Status Confirmed
94 – Cleanup-Related Adjustment
💡 Pro Tip: If payment amounts shift unexpectedly, check ARC first. It's your audit trail.
🆕 Highlight: Part D Default Risk Factor Code (Field 87)
This field identifies default RAF logic when a beneficiary has less than 12 months of Medicare Part A entitlement or insufficient RAS data.
📅 Code Logic by Period:
➤ For January 2011–Dec 2024:
0 = Not ESRD, Not Low Income, Not Originally Disabled
5 = ESRD, Low Income, Not Originally Disabled
7 = ESRD, Low Income, Originally Disabled
(And other combinations for Low Income, ESRD, and disability flags)
➤ NEW: Starting January 2025:
A = Not ESRD, Not Low Income, Not Originally Disabled, MAPD
F = ESRD, Low Income, Originally Disabled, MAPD
P = ESRD, Low Income, Originally Disabled, PDP
N = Not ESRD, Low Income, Not Originally Disabled, PDP
(More combinations included for full classification)
This code helps determine how the system calculates RAF when claims data is missing or eligibility is partial.
📌 Fields 88–90: Monthly Payment or Adjustment Rates
CMS uses county-level benchmarks to calculate payment. These fields show what rate was applied:
Field 88 – Part A Rate
Monthly Part A state/county payment or adjustment rate.Field 89 – Part B Rate
Monthly Part B state/county payment or adjustment rate.Field 90 – Part D Rate
Monthly Part D payment or adjustment rate.
If you're reconciling rate changes or benchmarking CMS payments, these fields tell you the base amounts before adjustments.
🛠️ Pro Tips for Analysts & Coders
Here’s how to use the MMR to tighten accuracy, audits, and payments:
✅ Always monitor ARC Codes (Field 28):
They're your "why" for retroactive payments, flags, and cleanups.
✅ Review Cleanup ID (Field 91):
Tracks systemic adjustments or RAS audit overpayments.
✅ Track RAF Changes with Fields 24–26, 46, 87:
Identify if a diagnosis, plan status, or demographic change affected the RAF.
✅ Cross-Reference Date Fields (Fields 29–30):
Make sure the start and end dates of payment match ARC context.
✅ Export MMR into Excel or Power BI:
Create dashboards for ARC trend analysis or RAF monitoring by plan or segment.
🧩 V28 Coding & MMR Impacts
CMS's V28 model has eliminated 2,200+ ICD-10 codes from HCC mapping. This means:
You’ll see more RAF recalibrations from vague to specific codes (E11.69 → E11.22 or E11.319)
ARC 25, 26, 37, and 41 might appear more often as RAF updates ripple through
This makes your documentation and coding more critical than ever — and the MMR a must-watch file each month.
🔚 Final Word: Know Your MMR, Own Your Accuracy
The MMR isn’t just a file — it’s the pulse of your plan’s payments. By mastering its structure, tracking ARC and RAF fields, and understanding the changes tied to diagnosis and dual-status logic, you’ll boost your team’s confidence and compliance.
🎁 Bonus Resources