March 16 – S-Corp (1120-S) & Partnership (1065) (or file extension)
April 15 – Individual (1040) & C-Corporation (1120) (or file extension)
May 15 – Non-Profit (990) (or file extension)
September 15 – Extended S-Corp (1120-S) or Partnership (1065)
October 15 – Extended Individual (1040) & C-Corporation (1120)
November 15 – Extended Non-Profit (990)

April 15, June 15, September 15, January 15 – Quarterly Estimates