Once ZIP Codes were translated into automation-readable barcodes, the USPS and mailing companies began working to pack more and more information into those codes. The codes evolved into the USPS’s Intelligent Mail Barcode system. The original 5-digit ZIP code is now 31-digits of information tucked into 65 bars in each code.
The 31 digits include ZIP Code information other data that can reveal how the mail was presorted, whether it is first-class mail or a periodical, the business sending each piece, and automatic address forwarding information.
The barcode also permits tracking of individual pieces of mail. When you return a pre-addressed business reply by mail, businesses can forecast when it will arrive. All this saves companies money, makes their business more predictable, speeds mail delivery time, and makes the postal system even more efficient—and efficiency is important, considering that half a billion pieces of mail flow through the system each day.