This field in the Open Item Maintenance window is a note about this transaction.
For example:
You are adding an adjustment to an account. In the Reference field, you type Correction to doc #1533 to describe why you are making the adjustment.
The system automatically updates this field when you enter certain information in POS.
If you enter something in the Reference field (on the Big Header), the system updates the Reference field in the Open Item Maintenance window.
If you don't enter a reference, but you enter a purchase order in the PO # field, the system updates the Reference field in the Open Item Maintenance window with the PO #.
If you don't enter a reference or a PO #, but the Build Order Reference field in Function MIV (Modify Invoice Constants) is Y, the system updates the Reference field in the Open Item Maintenance window with the order #.
This field is alphanumeric. You can enter up to 30 letters and numbers.