Medicaid & CHIP Research Files

State Medicaid and CHIP agencies collect enrollment and claims data for persons enrolled in Medicaid and the Children’s Health Insurance Program (CHIP). Beginning in 1999, the Centers for Medicare & Medicaid Services (CMS) required all states and the District of Columbia to submit their data via the Medicaid Statistical Information System (MSIS). Because Medicaid and CHIP programs vary by state, CMS required states to convert their data into a standard MSIS format. More recently, in an effort to enhance reporting for these programs, CMS replaced MSIS reporting with reporting in the Transformed Medicaid and CHIP Statistical Information System (T-MSIS).

T-MSIS submissions expand the data that state Medicaid and CHIP agencies report to CMS while improving the data’s quality and timeliness. T-MSIS differs from MSIS in the following ways:

  • Data are reported monthly instead of quarterly
  • Requires the reporting of CHIP (Title XXI) data
  • Expanded and modified the range of data elements states report
  • Files submitted increased from five to eight, adding files for man­aged care plans, providers, and third-party liability

CMS uses the raw MSIS and T-MSIS data to develop research files: Medicaid Analytic eXtract (MAX) and T-MSIS Analytic Files (TAF). The transition from MSIS to T-MSIS did not happen simul­taneously for all states. The majority of states transitioned to T-MSIS between 2013 and 2015. Consequently, CMS can offer one of two distinct research file products, depending on the year and state: Medicaid Analytic eXtracts (MAX) or T-MSIS Analytic Files (TAF). Both the MAX and TAF organize the data in a manner that make them easier for researchers to use for analysis.