As a C corporation, your tax deadlines are different than those for other business entities. You'll need to file your annual return by the 15th day of the 4th month after your fiscal year ends. For example, if your fiscal year ends on December 31, you'll need to file your return by April 15 of the following year.
If you're required to make estimated tax payments, they're due on the 15th day of the 4th, 6th, 9th, and 12th months of your fiscal year. So if your fiscal year ends on December 31, your estimated tax payments would be due on April 15, June 15, September 15, and December 15.
If you don't file your return or pay your taxes by the due date, you may be subject to penalties and interest. So it's important to know when your deadlines are and to plan ahead so that you can meet them.
If you have any questions about your tax deadlines, you should speak to a tax advisor or accountant. They can help you ensure that you're meeting all of your obligations and help you plan for any upcoming deadlines.