Do I enter 401(k) payments of quarterly dividends from employer stock, with a 1099-R, under Investments and Savings, or under 401(k) plan withdrawals?

[dmertz]

If these are reportable at all, they are reported to you by the plan on Form 1099-R with code U.  Enter the Form 1099-R under IRA, 401(k), Pension Plan Withdrawals.  If they dividends are retained in the 401(k) rather than being paid out to you and you receive no Form 1099-R, they are not reportable at all.

[DanaB27]

If you received a 1099-R then you will enter it in the retirement section:

1. Click on "Search" on the top right and type “1099-R”  
2. Click on “Jump to 1099-R”
3. Click "Continue" and enter the information from your 1099-R