Field help (LNDRTNDAT1) 

The 'loan return' date is initialized by the 'loan return' date defined in the order if it is a delivery coming from an order. Otherwise, it is not initialized and must be entered manually. This date is used if required, to invoice a loan delivery from the moment the 'loan date' is exceeded and the loaned goods have still not been returned by the customer. This date must be greater than or equal to the 'delivery date'.