Tax Calendar The Department of Revenue works with the IRS to provide information that is relevant to both agencies. The business tax calendar, produced in conjunction with the IRS, aims to help businesses keep up with important reporting dates for the IRS and DOR. Please note that not all dues dates for every tax type are included on this calendar. Due dates and filings pertaining to the North Carolina Department of Revenue are highlighted in blue. Due dates and filings pertaining to the Internal Revenue Service are highlighted in green.