Payment promise (3)
I believe the answer is:
iou
(Other definitions for iou that I've seen before include "Creditor's note" , "Debt note (abbr.)" , "Promise to pay in vowels" , "Debtor's note" , "Proof of debt" .)
I believe the answer is:
iou
(Other definitions for iou that I've seen before include "Creditor's note" , "Debt note (abbr.)" , "Promise to pay in vowels" , "Debtor's note" , "Proof of debt" .)