Deductions & credits

Your 401K contributions are not included in Box 1 of your W-2, so they are never included in your taxable income.  Same with health insurance you paid with pre-tax dollars.  Any medical premiums you pay with pretax dollars aren't counted in your taxable income.  When your employer prepares your W-2, your employer won't include these premiums in box 1, so you can see on your W-2 how those costs reduce your taxable income.    You will see them in box 12 of your W-2, but not in Box 1.    The income is Box 1 is subject to federal income tax, but your 401K contributions and pre-tax employer sponsored medical premiums will not be included in that number.   

So, you won't see TurboTax lowering your taxable income for those items since they were never in your taxable income to start with.  If you have medical premiums you paid with post-tax dollars, you will need to itemize deductions on Schedule A to see any tax benefit.  

To deduct unreimbursed, out-of-pocket medical, dental, and vision costs on your federal return:

• You must take the itemized deduction;
• The expenses for you, your jointly-filing spouse, and your dependent(s) must exceed 7.5% of your AGI (adjusted gross income); and
• Only the portion above and beyond 7.5% of your AGI is deductible.