file a application for condonation of delay to the department if you have pending refunds or carry forward of losses, to file the return for respective years.
I have no pending refunds & I dont have losses to c/f. I have income below taxable limit, no tax liability, but I want to file return as I need to submit last 3 years ITR ack for some special purpose. Can I file returns for FY 2017-18 & FY 2016-17 NOW.