I have two sources for this. See both listed below in web references. The first lists 墊付國內票款 with（應收客票融資）next to it, implying these are the same meaning. The term 墊付國內票款 is defined in the second web reference, and it can be inferred that, they way this is used on several different websites I've found, the meaning is invoices that have been collected from clients (in your example sentence, the invoices have therefore expired, moreover, not enough funds were deposited, so they could not be paid/cashed out).