The present invention relates to a method and system that use data tags to track tasks in applications to provide Object-to-Object (OTO) services. A first application data tag is issued by a data tag server as in an OTO service platform in response to an initiation of a first application by a first initiator. The first data tag specifies at least one first task for fulfilling a first service. The first application data tag is scanned by a first user terminal by a first participant. A first action data tag is issued by the data tag server. A first dynamically variable task data tag is issued by the data tag server to track the first task in the first action. The first dynamically variable task data tag is updated to record the completion of the first task in the first action when the first task is completed.