Embodiments of this application provide a charging method. The method includes that a session management function determines, a data flow within a protocol data unit, PDU, session and a charging key corresponding to the data flow within the PDU session, wherein a plurality of user plane functions are involved in the PDU session. For each of the plurality of user plane functions, the session management function sends to an online charging system, a quota request for a charging key without available quota for the UPF.