Field help (ACCDAT) 

This date represents the accounting date of the original transaction.
The accounting date makes it possible to determine the posting period of the accounting entries. It is initialized by default to the current date and it can be changed depending on the value of the PIHACCDAT - Accounting date modification parameter (ACH chapter, INV group).
This date is systematically controlled in order to verify that it belongs to an open and existing fiscal year.
If a problem occurs during the control, the user will need to enter a new date, irrespective of the parameter value.