You should check the traditional IRA box because the SIMPLE IRA is a type of traditional IRA, but you do not report in this section any contributions you made to the SIMPLE IRA. Enter amounts shown in box 12 of your W-2 (with code S for a SIMPLE IRA salary deferral) only in box 12 of TurboTax's W-2 form, nowhere else in TurboTax.
