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. The 941 report is your quarterly federal payroll tax return. Learn how to file IRS Form 941 for quarterly federal tax returns. Our comprehensive guide covers due dates, penalties, COVID-19 relief measures, and more.