What was taken from the distribution was tax withholding. Tax withholding is simply a down-payment against the tax liability eventually calculated on your tax return. The actual increment in your tax liability resulting from the 401(k) distribution is not determined until you prepare your tax return. When you enter the Form 1099-R into TurboTax, the federal tax withholding shown in box 4 of the Form 1099-R is credited on Form 1040 line 25b to be subtracted from your overall tax liability.
