Visit ttax.in for Due Date of at one place. Due Date of GST Annual Return of FY2018-19 extended to 31st December,2020. Due Date of Tax Audit of AY 2020-21 extended to 31st December,2020. Due Date of Income Tax Return(unaudited) of AY 2020-21extended to 31st December,2020. Due Date of Income Tax Return(audited) of AY 2020-21extended to 31st January,2020.