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CMS Guidance: Best Practice for Reporting CHIP-CODE in the T-MSIS Eligible File

Guidance History

Date Description of Change
6/21/2016 Original guidance issued
03/23/2021 Added language to clarify references to the “Medicaid Expansion CHIP” population as opposed to the general “Medicaid expansion” population and removed outdated table of CHIP-CODE valid values

Brief Issue Description

This best practice document outlines the challenges states have faced when reporting the CHIP-CODE data element in the T-MSIS Eligible file. CHIP-CODE is used to distinguish among Medicaid, Medicaid Expansion CHIP, and Separate CHIP populations when looking at enrollment and utilization data.

Background Discussion


Created as part of the Balanced Budget Act of 1997, the Children's Health Insurance Program (CHIP) builds on Medicaid to provide insurance coverage to uninsured, low-income children in families whose income is above Medicaid income-eligibility thresholds. States may use CHIP funds to expand their Medicaid programs (Medicaid Expansion CHIP), create a program separate from their existing Medicaid programs (Separate CHIP), or adopt a combination of both approaches. Although Congress provided states with significant flexibility in program implementation and characteristics, prior to T-MSIS states were required to report complete, person-level eligibility and claims data for enrollees in Medicaid Expansion CHIP programs to the Medicaid and CHIP Statistical Information System (MSIS). States had the option to include Separate CHIP enrollees as part of their MSIS reporting, and those states that wished to do so submitted only a subset of eligibility data elements (and excluded all claims information).[1]On August 4, 2010, the Center for Medicaid and CHIP Services (CMCS), part of the Centers for Medicare & Medicaid Services (CMS), issued a revised MSIS Data Dictionary (Release 3.1), which provided instructions to states for submitting complete, Separate CHIP eligibility and claims data effective October 1, 2010. The release encouraged states to provide complete reporting as soon as possible after this date; however, several states did not move to full Separate CHIP reporting under MSIS.

Under T-MSIS states are expected to report complete data on eligible data elements for both Medicaid Expansion CHIP and Separate CHIP enrollees. This full reporting in T-MSIS ensures that CHIP has a nationwide, person-based data set, providing much more flexibility for data analysis, such as tracking when low-income children move between these different programs as their eligibility circumstances change. These more complete data offer researchers a more sophisticated understanding of CHIP enrollment and utilization patterns and how they compare to Medicaid.


Data users rely on the T-MSIS data element CHIP-CODE to distinguish among Medicaid, Medicaid Expansion CHIP, and Separate CHIP populations when looking at enrollment and utilization data. It is imperative that states provide reliable data in this field, especially because the CHIP-CODE field is in the VARIABLE-DEMOGRAPHICS-ELIGIBILITY-ELG00003 record segment, which is separate from the individual's historical and active enrollment periods that are under the ENROLLMENT-TIME-SPAN-SEGMENT-ELG00021 record segment. To ensure that people are properly assigned to the correct codes, states must understand their own unique programs and upstream systems to assign enrollees to one of these CHIP-CODES values:

  • '1' = Individual was Medicaid-eligible, but was not included in either Medicaid Expansion CHIP or a separate Title XXI CHIP for the month. These include blind and disabled people and low-income families with dependent children.
  • '2' = Individual was included in Medicaid Expansion CHIP and subject to enhanced federal matching for the month. States with Medicaid-Expansion CHIP programs have built upon existing Medicaid programs to include low-income children whose family incomes are above Medicaid income eligibility thresholds.
  • '3' = Individual was not Medicaid Expansion CHIP eligible, but was included in a separate Title XXI CHIP for the month. States using Separate CHIP have used CHIP funds to create separate programs outside of their Medicaid programs.

A great challenge for many states is bridging various data systems that are often administered by different departments or housed in different systems, making it more difficult to obtain and reconcile the data needed for T-MSIS reporting. This might be particularly true for states with a Separate CHIP program because it is not part of the states' regular Medicaid operations.

CMS Guidance

States whose CHIP data originate across separate data systems have to match, merge, and reconcile data from these different systems to provide nonconcurrent values reported to CHIP-CODE. States should make sure that their CHIP-CODE data are reliable and consistent with other data fields. For example, Medicaid Expansion CHIP or Separate CHIP enrollees are not expected to be reported with RESTRICTED-BENEFITS-CODE = '3', which indicates benefits restricted to Medicare cost-sharing expenses.

As a way of assessing data quality and completeness, states can compare T-MSIS CHIP counts with enrollment information reported to the CHIP Statistical Enrollment Data System (SEDS), which includes CHIP enrollment counts submitted by states to CMS on a quarterly basis and can be considered an important source for validating T-MSIS data. We generally expect the counts of Medicaid Expansion CHIP and Separate CHIP enrollees in T-MSIS to be reasonably close to the counts reported to the CHIP SEDS reporting system for CHIP.[2]When these counts differ, it is worth exploring possible causes of the divergence. Sometimes there is a reasonable explanation (for example, some states might report unborn infants as children in CHIP SEDS, but capture them under the MSIS IDs of their pregnant mothers in T-MSIS), but other times it might lead to detection of an error in state reporting, whether on the T-MSIS or the CHIP SEDS side.

[1] The subset of monthly fields included only the CHIP-CODE and the state-specific eligibility group. Because these beneficiaries were not considered eligible for regular Medicaid, the rest of the monthly fields were 0-filled (such as Maintenance Assistance Status, Basis of Eligibility, Restricted Benefits Flag, and so on). States were encouraged to report as many of the root fields in the MSIS eligibility file as possible, such as MSIS ID, date of birth, and race/ethnicity.

[2] For comparison purposes, please note that CHIP SEDS counts are provided in quarterly enrollment counts.

T-MSIS File Type
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