Abstract: According to an aspect, there is provided a method for generating unique identifiers by an identifier management system. First, the identifier management system receives from a terminal device via a communications network a first request for a unique identifier for a first set of one or more items of the same type. The first request comprises at least an identifier for the type of the first set and an expiration date for the first set. Then, the identifier management system generates a first unique identifier for the first set based at least on the identifier for the type of the first set, a first time stamp corresponding to a current time and the expiration date. The identifier management system stories the first unique identifier to a database 10 and transmits the first unique identifier for the first set to the terminal device via the communications network.