I sell on Ebay and created customer Ebay Sells with one invoice every month. I tag my Paypal payments to customer but I think it would be easier tag it straight to the invoice (with future date like 31). It is possible to do something similar in Quickfile.
At the moment the credit allocation works on a FIFO basis (First in, First Out). So we don’t have the ability right now to nominate prepayments that should be assigned to a specific invoice. Any prepayment allocation is initiated from the invoice preview screen by logging a payment and selecting the credit option.
However if this is something that proves to be a popular request we can take another look. For now I’ve moved this post to a “feature request”.