Mandatory fields allow you to define items that are mandatory for any window in SAP Business One. This can be done at header and/or column level.
Right-click configuration™
To quickly get going go to the window you wish to make something mandatory, right-click it and choose Make this field / column mandatory.
Alternative you can go to: Administration > Add-Ons > B1 Usability Package > Module Configuration > Mandatory Fields: Configuration.