If you formed a C corporation in the United States, then your corporation will need to file an annual federal tax return. However, whereas an individual person or even an LLC must generally file their federal tax return for each calendar year, a C corporation has the option to use a tax year that doesn’t correspond to the calendar year. So how do you know when a C corporation has to file its first tax return?

A newly formed C corporation may choose as its tax year any period of 12 consecutive months that ends on the last day of a month, and the corporation must file its first federal tax return for that tax year by the 15th day of the fourth month following the end of that tax year.

Importantly though, the first tax year is often shorter than a full year since the company’s first tax year effectively begins on the day the company was incorporated (which is probably not the first day of a month) rather than the start of the chosen 12 month period, and the first tax year ends the first time the chosen ending month comes around.

For example, if you form a new C corporation on July 10 and choose a tax year that ends in August, then your first tax year would be one month and 21 days, ending August 31st of that same calendar year. The corporation’s federal tax return would then be due December 15 of that calendar year.

As a second example, suppose you form a new C corporation on September 20 and elect a tax year that ends in August. Then the corporation’s first tax year would be 11 months and 10 days long, ending on August 31st of the next calendar year, and the corporation’s first federal tax return would be due December 15 (also of that next calendar year after the company’s incorporation).

Corporate Tax Year Exceptions

In certain situations such as if a corporation is a consulting, accounting, or other company that primarily sells the services provided by employee-owners, then the corporation may have to use the calendar year as its tax year (see IRS publication 538 for details if you think you might fall into this category).

State Corporate Income Tax Returns

The situation for state tax returns is unfortunately more complicated than it is for federal tax returns. Firstly, different states have different deadlines, with some allowing for a choice of tax year that respects your federal choice of tax year and others not. Secondly, some states treat corporations differently depending on whether the corporation has a physical presence (e.g. a rented office, an employee, etc) in the state or if the corporation is only incorporated in the state. Finally, different states sometimes use different terminology for taxes and tax returns that are similar to income tax returns.

For example, Delaware imposes an “income tax” and a requirement to file an “income tax return” only on corporations that have a real presence in the state, and that return must be filed according to the same deadline as the federal tax return. However, Delaware also imposes a “franchise tax” on all corporations incorporated in Delaware, whether or not those companies have any actual presence in the state, and that tax must be paid along with a filed “annual report” by a different deadline which does not depend upon a corporation’s federal tax year.

The corporate filing deadlines for five of the most common states for incorporation are summarized in the table below.

State	Filing Deadline	Additional Info
Delaware	March 1 (for Franchise Taxes & Annual Report) Same as federal deadline (for corporate income tax & corporate income tax return)	Delaware franchise tax info page Delaware franchise tax & annual report portal Delaware corporate income tax info page Note: Delaware’s corporate income tax only applies to corporations with a real presence in the state, whereas its franchise tax applies also to all corporations incorporated in the state.
California	Same as federal deadline	California business due dates info page California Code: Corporation Tax Law Note: California uses the term ‘franchise tax’ to have the same meaning as ‘corporate income tax’
Texas	May 15	Texas franchise tax overview There is no separate ‘corporate income tax’ other than the ‘franchise tax’ in Texas.
Washington	April 15	Washington business & occupation tax FAQ Note: Washington’s “business & occupation” tax is actually a “gross receipts” tax and is levied against the entire revenue of a corporation rather than just its net income
Florida	The later of: 1. For tax years ending June 30, the 1st day of the 4th month following the close of the tax year, or for all any other tax year, the 1st day of the 5th month following the close of the tax year. and 2. The 15th day following the federal due date (without extension)	Florida corporate income tax info page Florida uses the terms ‘corporate income tax’ and ‘franchise tax’ interchangeably.