Need information about FI document with header and no items

Hello Experts!

I need your help for understanding the following subject :

How is it possible when using F.13 to obtain a fi document with header without items sometimes,

and fi document with header and items anothers times?

We didn't saw/found customizing topics about that ( to enable or not header without items) Some exists?

The only difference in the two cases are the document's type involded which are not the same.

Regards,

Josiane