Can I contribute to a Simple IRA for 2016 if I just opened it March 2017?

[dmertz · Accepted solution]

No.  To receive a contribution for 2016, the SIMPLE IRA had to be established by October 1, 2016 (or, if you business came into existence after October 1, as soon as administratively feasible before the end of 2016).

Your only option for establishing a retirement plan after the end of 2016 to receive a self-employed retirement contribution for 2016 is a SEP plan.