Ajuda p/o campo (PYHVCRLIN) 

Specify the open item to be allocated to the payment line by specifying its type and journal number. This information can be entered only if the payment attribute entered is 'chargeable' ('matchable').
It enables payment posting to perform for example the matching between payment and paid invoice.
The document type and the document can be directly selected using one of the two left lists: 'Open items' or 'Grouped open items' The selected open item must:

The document type given by default comes from the payment attribute. The document number corresponds either to the invoice number of to an open item on the invoice (case of a multi open item invoice). It can also be an order journal type (see general parameters BPSORDTYP - Supplier order doc type and BPCORDTYP - Customer order doc type) and in that case it will be necessary to enter the order number. No matching is triggered when a payment is reconciled to an order.

In the specific case of SDD: the open items to be allocated must have the same mandate reference as the one selected in the header.