A Delaware C-corporation is required to file:Federal tax return, Form 1120 (see Instructions for Form 1120 (2023) and http://www.irs.gov/pub/irs-pdf/f... for the form itself).If you conduct business in Delaware, a Delaware Corporate tax return, Form 1100 (see http://revenue.delaware.gov/serv... for the instructions and http://revenue.delaware.gov/serv... for the form itself).If you do not conduct business in Delaware, you must pay the Delaware franchise tax and file an Annual Report - see Division of Corporations - Franchise Tax Calculations for the methods of calculating the franchise tax and Division of Corporations - Online Services to file and pay online.In my opinion, corporate tax preparation is not something you should try to take on yourself, hire a professional.