An image forming system includes a terminal apparatus and an image forming apparatus executing a process in response to a request from the terminal apparatus. The terminal apparatus sends user identification information to the image forming apparatus, receives from the image forming apparatus a token issued to a user logging into the image forming apparatus, and sends a service request associated with the token to the image forming apparatus. The image forming apparatus includes a network processing unit that communicates data using a predetermined protocol with the terminal apparatus; a login processing unit that permits the user to log in when the user identification information is valid and sends the token to the terminal apparatus; a determination unit that determines whether the token is valid upon receipt of the service request; and a service providing unit that executes a process designated by the service request when the token is valid.