Definitions for "Postage Due"
A term used to describe items of mail on which postage has been either unpaid or short paid or which requires additional postage for delivery. (port dû)
A stamp issued to collect unpaid postage.
Used to collect fees on unpaid/underpaid letters  Postmark A mark applied to a letter etc, by the postal authority, to indicate date/time of posting, transit, arrival or special service  Precancel A stamp postmarked prior to use in bulk mail preparation