Unlike the safe harbor non-elective contribution, you still need notice and you still need one in place if you want one for 2021 by December 1.
While non-elective safe harbor formulas no longer need notice and no longer need to be in place until during or even after the plan years are over, the changes made by the SECURE Act are not applicable for safe harbor matching contributions. The reason why is safe harbor match is tied to deferrals and participants should have a right to decide if and how much they are willing to defer, to benefit from the safe harbor match.
