If you are a participant in an employer-sponsored qualified retirement plan, such as a 401(k), or you have a Traditional IRA or a Roth IRA, and you received money from those plans during 2016 (other than borrowing from a 401(k)), the money you received is called a "distribution" and must be reported on your Federal income tax return. The trustee of the plan should issue you a Form 1099-R with all the information you need to report that distribution.