Periodic Returns. Quarter-monthly Form Mo 941P must be mailed, by employers withholding $9,000 or more for any month, within 3 banking days or received by the Department within 4 banking days after end of quarter-monthly period (first 7 days of calendar month, 8th to 15th day, 16th to 22nd day, and 23rd day to end of month. A monthly report to reconcile quarter-monthly payments and pay any taxes owed is due by the 15th day of the succeeding month on Form Mo 941W, except for the third month of a quarter, which is due by the last day of the succeeding month. Monthly (Form Mo 941) for employers withholding $50 or more per month for at least 2 months, due by 15th of the following month. Returns for the last month of a quarter due by last day of following month. Quarterly for employers not required to file monthly who withhold at least $20 per quarter during at least 1 of the preceding 4 quarters, on Form Mo 941, due by end of month following quarter. Annually (Form Mo 941) by January 31 where less than $20 per quarter was withheld.

Annual Reconciliation Returns. Form Mo 941R due by January 31.

Timely Filing. Returns and reports that fall due on Saturday, Sunday, or a legal holiday are considered timely filed if filed on the next succeeding day which is not a Saturday, Sunday or legal holiday. A return is deemed timely filed if postmarked on the date the return is due. If there is both a postage meter date and a U.S. postmark, the postmark will determine the date of delivery. For any return, document, or payment sent by U.S. registered mail, the date of registration is treated as the postmark date. If sent by certified mail and the sender's receipt is postmarked by the postal employee, the date of the postmark on the receipt is treated as the postmark date.