A data element to capture the various identifiers assigned to Medicaid and CHIP beneficiary by various entities. The specific type of identifier is shown in the corresponding value in the Eligible Identifier Type data element. States should provide all Old MSIS Identification Number with Eligible Identifier Type = 2 to T-MSIS in case the state changes the MSIS Identification Number of a beneficiary. The state should submit updates to T-MSIS whenever an identifier is retired or issued. States should provide Old MSIS Identification Number with Reason for Change = 'MERGE' to T-MSIS if the state was reporting multiple MSIS Identification Numbers for a single beneficiary and merges them under a single MSIS Identification Number. States should provide Old MSIS Identification Number with Reason for Change = 'UNMERGE' to T-MSIS if the state unmerges a beneficiary from another beneficiary. For example, if a newborn child is originally reported with the mother's MSIS Identification Number and is then assigned a different MSIS Identification Number. States should provide Old MSIS Identification Number with Reason for Change = 'LSE' to T-MSIS if the state assigns a new MSIS Identification Number to any beneficiaries during large system enhancement in state MMIS. States should provide Old MSIS Identification Number with Reason for Change = 'TCAM' to T-MSIS if the Medicaid and Separate CHIP programs use different MSIS Identifier Number schemas and beneficiaries are transferred from CHIP to Medicaid or from Medicaid to CHIP and a new MSIS Identification Number is issued.

1. Value must be 20 characters or less
2. Mandatory
3. Must not contain a pipe or asterisk symbol