Grouping of Payment Items in Automatic Payment Program (F110)

When executing an Automatic Payment program (F110), Various open items can be grouped together to be paid with a single payment document.
The grouping of open items for payment is carried out based on the fields in structure ZHLG1. Items are grouped only if all the fields in this structure are identical

for more details on open item grouping, refer to the following SAP Note
Note 164835 - F110: Clearing credit memos and invoices