If there is a code "S" in box 12 on your W-2, then this is the amount contributed to your Simple IRA.
In this case, your tax break is that this code S amount is not in included in Wages in boxes 1, 3, or 5, because employer contributions to a Simple IRA are not subject to federal income tax, social security tax, or Medicare tax.
In other words, your employer is making tax-free contributions to your retirement.
