This relates to Accounts Receivable.
In South Africa we age our documents based on the document date (i.e. Debtors Aged Analysis.) We are on version 4.6C, and our problem arise when we process a part receipt against an Invoice the remainder of the Invoice amount gets lumped into our CURRENT bucket ie; 0 to 30 days outstanding, even though the Invoice being paid is a 90 day old document.
Example Invoice = R1000 in 90 days.
customer pays R700
The remaining R300 goes into current and does not stay in the 90 day column. Could this be because our previous posting periods are closed at the time of processing the receipt?
I struggle with the same issue. I believe you are right that closed periods prevent the partial payment from posting directly against the invoice. I am not brave enough to re-open closed periods because of all the other bad things that could happen, so I just live with the partial payment timing problems.
One scenario we tested with a customer who had a large balance with terms of twelve equal monthly installments was to delete the prior billing document and create a new one for the remaining balance each time they paid. This was quite labor intensive, but it did keep their outstanding balance in the "current" column. I do not necessarily recommend this, but it is an option.
I've been experimenting with changing the baseline date ("Bline Date" is the field name on the SAP screen) to see if that will keep the money current on the aging for customers with extended payment terms. Early results are promising. Try it with your invoices and payments to see if it works for you.