Matching Form submissions to Form payments

I am trying to identify an efficient way to match Form payments with form submissions -- so that I know who paid, and who selected "bill me later".  The form export fields do not inlcude payment info and the payment export does not conveniently track back to submissions via something like a transaction reference number.  Am I missing something obvious?



Most efficient solution would be field that exports with the Form Date Submissions that says "Paid $x" or "Bill me".  This would not have to convey credit card info of any sort.   Simply put the relevant transaction info in the same export file with the form submission data/fields.  



The lack of this ability causes a great deal of additional labor/time that could be avoided.