Since it is already past March 15, 2017, it is too late for a calendar-year S corp to now request a filing extension for a 2016 tax return. Unless your S corp did so by March 15, 2017, the opportunity for your S corp to make a SEP contribution for 2016 has been lost. If your S corp did request a filing extension by March 15, your S corp has until September 15, 2017 to make your SEP contribution.
