Mailing addresses for Forms 941 ; Department of the Treasury Internal Revenue Service Kansas City, MO 64999-0005. Internal Revenue Service PO Box 806532Overpayment as a nonemployee, file Form 941 for each delinquent quarter. This guide will teach tax filers the basics of the 941 tax form along with detailed instructions to help you fill it out for your small business. To start, download Form 941-X from the Internal Revenue Service website. If an overpayment has been made, we will issue a credit for the overpayment amount. This article breaks down everything you need to know about IRS Form 941 and how to complete it with ease.