Generally, a corporation must file its income tax return by the 15th day of the 3rd month after the end of its tax year. A new corporation filing a short-period return must generally file by the 15th day of the 3rd month after the short period ends. A corporation that has dissolved must generally file by the 15th day of the 3rd month after the date it dissolved.
If the due date falls on a Saturday, Sunday, or legal holiday, the corporation can file on the next business day.
Extension of Time To File. Form 7004 Application for Automatic Extension of Time To File Certain Business Income Tax, Information, and Other Returns, to request a 6-month extension of time to file. Generally, the corporation must file Form 7004 by the regular due date of the return.