An image processing apparatus includes an input unit configured to input image data and is communicably connected to an external apparatus via a network, wherein a document with a predetermined form is obtained from the external apparatus via the network and a screen based on the document obtained by the obtaining unit is displayed. Image data input by the input unit according to instructions from a user via the screen displayed with the display unit is transmitted. At this time, determination is made regarding the size of image data that can be processed by the transmission destination of the image data, and based on the determination results thereof, control is performed such that the image data according to the size of image data that can be processed by the transmission destination is input by the input unit.