#Filing an ITR for FY 2019-20 is mandatory if: 1. The individual's total income exceeds the maximum amount not chargeable to tax. The basic exemption limit for FY 2019-20 is Rs 3 lakh for senior citizens (aged 60 years or more but less than 80 years), Rs 5 lakh for super senior citizens (aged 80 years or more), and Rs 2.5 lakh for others; 2.The individual needs to claim an income tax refund of TDS or TCS or carry forward loss 3. The individual has undertaken specific transactions viz. (a) payment of electricity bill in excess of Rs 1 lakh during the FY (b) deposited more than Rs 1 crore in one or more current accounts during the FY or (c) spent more than Rs 2 lakh on overseas travel for self or any other person during the FY. 4. For firm and Company ect..it's mandatory to file Return
Ect...refer section 139 of Income tax Act, 1961 for more details
Other than these mandatory reasons, it is a good practice to file ITR since tax return as is required for visa applications, availing bank loans etc...