An image processing apparatus includes an internal receiving device, a communication unit, an image processing unit, and a controller. The internal receiving device may receive authentication information. The communication unit may communicate with an external receiving device to receive the authentication information. The image processing unit may perform at least one of image reading and image formation. The controller may determine one of the internal receiving device and the external receiving device is a first receiving device of the authentication information. The controller may also perform an authentication process based on the authentication information received from the first receiving device without performing the authentication process based on a second receiving device. The second receiving device is an other of the internal receiving device and the external receiving device.