Employers in Delaware must conform with these state rules relating to filing income tax withholding returns.
Periodic Returns. Eighth-monthly (Form W1-A) due by the third working day following the end of the deposit period. Quarterly (Form W-1Q) by the last day of the month following end of quarter.
Monthly (Form W-1) by 15th day of following month.
Annual Reconciliation Returns. Form W-3 due by last day of February.