If the data source you import items from contains Closing Balance information you can use this to update balances. Normally it is only necessary to import the Closing Balance. The Opening Balance will be used for validation purposes only. Balance data will normally require a new tag to be created to identify a line in the data source that contains the closing balance data. You will map fields within the data source to fields of Field Type Balance.
The basic information required to map for Closing Balance data is: