All tax deductions for December 2017 need to be deposited latest by 7th January 2018.
Filing of TDS Returns for the quarter ended December 2017 (FY:2017-18 Quarter 3) is already under way since 1st January and the last date is 31st January 2018.
Last date for filing TCS return is 15th January, 2018 and for issue of TCS certificate 30th January, 2018.