In transaction VF02 when you try to release a cancellation invoice to accounting (by clicking on the button with the green flag or pressing SHIFT+ F4) , instead of the creation of an accounting document the error message FF786 is issued:
A tax reporting date is missing, and should be entered.
The error message refers to note 1232484, which explains in detail the background of the new field BKPF-VATDATE.
To have this field available, the tax date will have to be first activated in the customizing of the company code (transaction OBY6):
Important to know is that the filling of the field is not done in the SD module. You can not find an entry possibility on the invoice, because this field is simply not existing there. The VATDATE is determined during the creation of the accounting document, in FI coding, by a BAdI VATDATE_VALUES (see in transaction SE18).
After the activation, when a new invoice is created, in the accounting document the field BKPF-VATDATE is automatically populated.
But what happens when you try to cancel an invoice that had been created before VATDATE activation?
The above shown error FF786 occurs when the so called new cancellation procedure with function module AC_DOCUMENT_REVERSE is executed by the system, and both accounting documents of the original invoice, and the one of the cancellation invoice are automatically cleared with each other. See
note 1259505 for a detailed explanation.
Now the problem in this case is the missing VATDATE in the accounting document of the original invoice, which should be cancelled:
This is the root cause of the error FF786, when a cancellation is performed with the new cancellation procedure, because in this case the VATDATE is copied from the accounting document of the original invoice:
Here, as the BKPF-VATDATE is not filled, no date can be assigned in the cancellation accounting document, which leads to the error FF786:
VATDATE is activated in customizing table T001 (transaction OBY6), the BKPF-VATDATE is empty, therefore error message FF786 occurs.
To avoid the error, one method would be to fill the BKPF-VATDATE in already created accounting documents. As in the PDF attachment of the already mentioned note 1232484 described on page 8, the migration tool GLO_VATDATE could be used for this purpose (enter this name in transaction SA38).
An alternative would be to force the system to execute the old cancellation procedure with function module AC_DOCUMENT_CREATE with the help of user-exit USEREXIT_FILL_XKOMK1 of include RV60BFZA, see note 339928.
With the old cancellation the BAdI VATDATE_VALUES can be executed, and BKPF-VATDATE filled according to your own logic.
Of course the disadvantage of the old cancellation procedure would be that you have to clear the accounting documents yourself.
The recommendation is therefore to use the migration tool and add VATDATE in already created accounting documents.