You can use infotype “0105 Communications”. Though it is called as communications, you can use it based on a subtype. The subtype is upto 4 characters and can be configured as you like. In the infotype you can have the subtype, and userid 30 char.
Examples of use of this infotype : a person’s logon id, passport number, driver lic.no., etc.
a)In IMG, navigate to Personnel Administration -> Communication.
Open “Create Communication types”
Alternatively, you can navigate as below:
Open IMG (trxn SPRO->F5),
b)Configure the subtypes.
This should do, for your purposes.