ISS Code 128

International Symbology Specification (ISS) Code 128 is a variant of the Code 128 barcode symbology that has an added feature that enables extended ASCII characters for non-English languages to be encoded. It is used as the basis of the GS1 Serial Shipping Container Code (SSCC) and other secondary symbols that use GS1 application identifiers. It is also used (with character set C) for the US Postal Service (USPS) Intelligent Mail (IM) Tray label system. USPS IM Tray barcodes contain 24 digits to uniquely identify the mailer and each tray, tub, and sack.

The Intelligent Mail Tray Label implementation is defined in the USPS-L-3216 Labels, Tray and Sack, Barcoded, 24-Digit, Intelligent Mail specification and further described in the USPS Intelligent Mail Tray Label - Technical Summary for Mailers: Basic, Full-Service, and Beyond document.

ISS Code 128 is defined in AIM BC4:1999 International Symbology Specification - Code 128.