General Instructions. Who must file Form M-941?Amount overpaid to be credited to next period. 10. Amount overpaid to be refunded. Overpayment as a nonemployee, file Form 941 for each delinquent quarter. If you are a monthly schedule depositor, complete the deposit schedule below; if you are a semiweekly schedule depositor, attach Schedule B (Form 941). This user's guide is designed to provide submitters, including Professional Tax Preparers (PTP) and third party payroll.