Mailing addresses for Forms 941 ; Department of the Treasury Internal Revenue Service Kansas City, MO 64999-0005. Internal Revenue Service PO Box 806532Bystep explanation on how to fill out Form 941. Overpayment as a nonemployee, file Form 941 for each delinquent quarter. This guide provides the basics of the 941 form, instructions to help you fill it out, and where you can get help meeting all your payroll tax obligations. What documentation is needed if I'm claiming an overpayment on an amended Form MO-941? When I did the 4th qtr 941 I had an overpayment. But when I run the 1st qtr report it does not pull forward, How do I fix it to show up?