Distributions from a 401k that are reported on a Form 1099-R are reported on Lines 16a and 16b of Form 1040.
Line 16a reports the total distribution amount and line 16b reports the taxable amount.
When you enter the Form 1099-R into TurboTax, the check box in Box 7 indicating that the distribution is from IRA/SEP/SIMPLE, along with the distribution code, is used to determine whether the distribution is reported on line 15 or line 16.
Also, amounts shown on the Form 1099-R for Federal tax withholdings is included on Line 64.
To go to the section of TurboTax to enter information from your Forms 1099-R, use these steps:
On the top row of the TurboTax online screen, click on Search (or for CD/downloaded TurboTax locate the search box in the upper right corner)
This opens a box where you can type in “1099-R” (be sure to enter exactly as shown here) and click the magnifying glass (or for CD/downloaded TurboTax, click Find)
The search results will give you an option to “Jump to 1099-R”
Click on the blue “Jump to 1099-R” link