This document describes South Korea's T-money system for electronic fare payment across multiple transportation modes. The system allows users to load funds onto a single T-money card that can be used to pay fares on buses, subways, and other transit modes. It also functions as an electronic wallet for non-transit purchases. Funds can be loaded onto T-money cards through offline methods at convenience stores or transit stations as well as online through users' mobile phones, the internet, or bank transfers. This unifies fare payment and provides interoperability across South Korea's different transit agencies and operators.