To assign a user name to tolerance group ( that we defined in transaction code OBA4 ) we need to do a configuration in SAP so that, when a user enter any transaction it should follow the rule that has been set for the group set for it.
To assign the user to tolerance group for employees follow the following path:
Path: SPRO > Financial Accounting > Financial Accounting Global Settings > Document > Line item > Assign User/Tolerance Group
T Code to assign: OB57
Click On new entries and enter your user name with the tolerance group then click on SAVE