Federal income taxes withheld from a retirement plan distribution, which are listed in box 4 of Form 1099-R, are claimed as a credit on your return against the taxes you owe; they’re reported as taxes that you’ve already paid for the year.
Items, such as interest, state and local income and sales taxes, charitable contributions, and medical deductions, claimed on Schedule A of Form 1040. Itemized deductions are subtracted from adjusted gross income to arrive at taxable income. The amount of itemized deductions is also subject to a reduction when adjusted gross income exceeds certain limits.