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Reporting Shared MSIS Identification Numbers (Eligibility)

Brief Issue Description

This document outlines the challenges states have faced when reporting eligibles that share an MSIS identification number (MSIS-IDENTIFICATION-NUM) and guidance for states’ reporting.

Background Discussion


According to the Centers for Medicare & Medicaid Services (CMS), MSIS identification numbers (MSIS IDs) (and/or Social Security numbers [SSNs]) in T-MSIS typically represent an individual with distinct demographic and eligibility information. MSIS IDs (and/or SSNs) also distinctly identify that individual over time, with the exception of individuals who have applied for but not yet received an SSN in an SSN-state (that is, a state that uses SSN as the primary distinct beneficiary identifier). This expectation is complicated by federal statute and variation in state assignment of distinct identifiers for children younger than 1 year of age.

Children born to mothers who are eligible for full Medicaid or pregnancy-related benefits are automatically eligible for Medicaid through their first birthday. These children are referred to as “deemed newborns” and are deemed eligible for Medicaid until the child’s first birthday without a separate application being filed on the child’s behalf or a separate eligibility determination. States are allowed1 to use the mother’s ID for coverage of the deemed newborn through the child’s first birthday. Assigning the deemed newborn a permanent unique ID that is distinct from the mother’s ID is optional until the child’s first birthday. If the state elects to transition the deemed newborn to his or her own ID during that first year, the transition must not negatively affect the child’s access to coverage.

Pregnant women who meet all Medicaid eligibility requirements, such as income and state residency, but who are not U.S. citizens and do not have an eligible immigration status, may receive Medicaid coverage for limited emergency services, including labor and delivery. Children born to such mothers are also eligible for Medicaid as deemed newborns. Unlike other deemed newborns, states are required to assign a separate ID to the deemed newborn at birth, if the mother was receiving Medicaid coverage of labor and delivery as emergency medical services. In this instance, the child receives full Medicaid coverage and may not be covered under the mother’s identification number because the mother is only covered by Medicaid for emergency medical services.

In some states, the unborn child of a pregnant woman who is not eligible for full Medicaid coverage due to her immigration status, but who is eligible for emergency only Medicaid may be eligible to receive coverage for prenatal care under the Title XXI Children’s Health Insurance Program. In cases in which a pregnant woman is eligible for emergency-only Medicaid coverage and her unborn child is eligible for prenatal benefits at the same time, some states use the mother’s MSIS ID, carrying with it all of the mother’s demographic information, for both the emergency-only Medicaid coverage and the unborn child’s prenatal benefit coverage. Other states assign a separate MSIS ID to the unborn child for the prenatal care coverage, which may have a combination of the mother’s demographics, the unborn child’s anticipated delivery due date, and/or missing information.


Assigning and maintaining primary identifiers for eligible individuals occurs far upstream of T-MSIS, typically in a state’s eligibility and enrollment system(s). As long as the state’s approach does not conflict with federal statutes or federally approved state Medicaid operating procedures, it is not required to split or combine eligibility records upstream of T-MSIS. Splitting or combining eligibility records during T-MSIS production at the state level poses risks to data integrity. According to a CMS letter (PDF, 57.71 KB) distributed to state health officials in 2009, states that opt to cover both the unborn child and pregnant women under the CHIP state plan are required to “uniquely identify enrollees so that there is no duplication of payment for services.” In other words an individual (mother, unborn child, or otherwise) must not be assigned more than one identifier—but it does not necessarily require that all mothers and their infant be assigned distinct identifiers.

The variation in how different states assign unique identifiers to mothers and children makes it challenging to validate the quality of the data and perform reliable comparative analysis. While, as stated above, splitting eligibility records during T-MSIS production poses risks to data integrity, using a single MSIS ID to track two individuals’ demographics and/or eligibility can make it very difficult for CMS to distinguish between valid and invalid data. For example, if the state uses the mother’s MSIS ID and the mother’s demographic data to report the eligibility group for the unborn child, then the mother’s date of birth, which is assigned to the unborn child, would conflict with the eligibility requirements for the unborn child’s coverage. On the other hand, reporting the unborn child’s anticipated delivery due date (which will sometime be in the future) or no date of birth at all can easily be mistaken for data quality issues, as states already have different methods of reporting dates of birth, which tend to deviate from the traditional interpretation of what a date of birth should represent. If the state uses the mother’s MSIS ID to report concurrent eligibility for the mother and child, then it appears as though that MSIS ID has duplicate coverage. These conflicts would be difficult to explain reliably if any confounding data quality issues are associated with that MSIS ID. Likewise, for children younger than 1 year of age, a state might report the demographics of both the mother and the child under the same MSIS ID, which, if the child were male, could result in a MSIS ID being assigned to a male and a female at the same time.

CMS Guidance

States are strongly encouraged to uniformly report data in accordance with T-MSIS data dictionary specifications to the greatest degree possible and clearly document in the state’s source-to-target-mapping where the state’s data vary from those specifications so that, at the very least, data users can adjust their analysis accordingly. Thorough documentation of a state’s unique administrative features can prevent misinterpretation and over-cleansing of data that can potentially lead to loss of useful information. While the specific manner in which states operationalize policy will impact how they best address these issues, the components of a T-MSIS eligibility record that require the greatest attention in relation to pregnant women, unborn children, mothers, and their deemed newborns younger than 1 year of age who share the same MSIS ID are PRIMARY-DEMOGRAPHICS segment data, VARIABLE-DEMOGRAPHICS segment data, ELIGIBILITY-GROUP, CONCEPTION-TO-BIRTH-IND, and RESTRICTED-BENEFITS-CODE (for limited benefit aliens). Further guidance and technical assistance will be provided after CMS collects data from more states to identify similarities and differences in data characteristics across states and trends and over time.

See [1] State Plans for Medical Assistance

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