Identifying Dual Eligible Medicare Beneficiaries in the Medicare Beneficiary Enrollment Files


For data years 2006 and forward, dually eligible Medicare beneficiaries are identified in the Medicare Master Beneficiary Summary File, Base segment. Initially available only as a RIF, this file was released as an LDS file in 2016. The monthly variable “Medicare-Medicaid Dual Eligibility” identifies dual status.

Dual eligibles are also identified in the Medicaid Analytic Extract (MAX) Personal Summary (PS) file.

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Dual eligible enrollees are Medicare enrollees that are receiving some form of assistance from their states’ Medicaid program. Dual beneficiaries may receive all or some of the following:

  • Medicare Part B premium assistance
  • Medicare cost sharing payment assistance
  • Eligibility for full Medicaid services

Detailed descriptions of the various, specific types of dual eligibility are found on the CMS web site. The MBSF variable “Medicare-Medicaid Dual Eligibility Status” occurs monthly. The values identify:

  • Qualified Medicare Beneficiaries (QMBs)
    • Medicare Part B Premium and cost-sharing assistance
    • With or without Medicaid benefits
  • Specified Low-Income Medicare Beneficiaries (SLMBs)
    • Medicare Part B Premium Assistance
    • With or without Medicaid benefits
  • Qualified Disabled and Working Individuals (QDWIs)
    • Medicaid only pays the Medicare Part A premium
    • Beneficiaries spend down assets to be eligible
  • Qualifying Individuals (Qis)
    • Medicaid paid Part B Premiums, effective 1/1/1998 to 12/31/2002
    • Beneficiaries spend down assets to be eligible
  • Medicaid Only Dual Eligibles, entitled to full Medicaid benefits but receive not cost-sharing or premium assistance

Prior to the development of the MBSF variable with the implementation of the Part D program, there was no reliable way to identify all dually eligible from Medicare enrollment files.

Statistics on the Dual Eligible Population are available from the Kaiser Family Foundation.