If you received retirement benefits from a pension plan etc. or took money from a retirement account like a 401k or IRA, you will receive a 1099R and it must be entered on your tax return. They have until January 31 to issue them. Often you can go on the plan's website to see them and/or print them out if you want to.
To enter your retirement income, Go to Federal> Wages and Income>Retirement Plans and Social Security>IRA 401 k) Pension Plan Withdrawals to enter your 1099R.