Valid Entries Lists are lists of values that are accepted for entry into most database fields. Fields that already display a Lookup List when [Ins] is pressed (such as Date fields, Tax Code, Department, etc.) do not support Valid Entries Lists.
See:
Using Valid Entries Lists
Creating A Valid Entries List
Valid Entries List File Format & Name
Valid Entries List File Names
Edit Valid Entries List Screen File Menu
Edit Valid Entries List Screen Settings Menu
Database List Editor