GS1 is the global standards body for item identification. Each country has its own local office that administers the licensing of Company Prefixes and GTINs. In the US, the local GS1 office is called GS1 US. Even though GS1 US is technically a monopoly, the GS1 system does provide trading partners the assurance of globally unique item identifiers. It is for this reason that retailers and marketplaces, such as Amazon, require suppliers to obtain GS1 UPC barcodes.