An electronic tax declaration system includes an input unit that receives financial information data to be declared; a data conversion unit that converts the received financial information data according to specifications of declaration data; a declaration data generation unit that adds a digital signature to the converted financial information data for generating declaration data and stores it into a storage; a declaration transmission unit that sends the declaration data to a regulator handling a tax; a declaration result reception unit that receives a declaration result of the declaration data from the regulator and stores it into the storage associated with the declaration data; and a loan application unit that creates loan application data by extracting the declaration data and the associated declaration result from the storage and adding a digital signature to them and sends the created loan application data to an external unit.