Federal income tax withholding reported on Form 1099-INT is entered in the same section as the interest income reported on that form. You will need to look for a check box on the screen that says something like, 'my form has more info than just box 1'. When you check that box, more options will open, including a place to enter Federal tax withheld.
Then, the amount withheld will automatically be taken into account on your return.
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