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“A calendar-year C corporation's federal income tax return is due on April 15.”
The conclusion
The ordinary federal filing deadline for a calendar-year C corporation is April 15. Federal law sets the deadline as the 15th day of the fourth month after year-end, and IRS guidance confirms the resulting date. If April 15 falls on a weekend or legal holiday, the filing deadline generally shifts to the next business day.
Caveats
- The operational deadline shifts to the next business day when April 15 falls on a weekend or legal holiday.
- An approved filing extension changes the return-filing deadline but generally not the deadline for paying tax owed.
- Special statutory rules may apply to certain corporations or unusual filing circumstances.
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Sources
Sources used in the analysis
the income tax return required under section 6012 of a domestic C corporation (as defined in section 1361(a)(2)) or of a foreign C corporation having an office or place of business in the United States shall be filed on or before the fifteenth day of the fourth month following the close of the taxable year.
The amendments to section 6072(b) of the Internal Revenue Code made by section 2006(a) of the Surface Transportation Act change the due date for filing an income tax return by a C corporation from the fifteenth day of the third month following the close of the taxable year (March 15 for calendar-year taxpayers) to the fifteenth day of the fourth month following the close of the taxable year (April 15 for calendar-year taxpayers).
The amendments to section 6072(b) of the Internal Revenue Code made by section 2006(a) of the Surface Transportation Act change the due date for filing an income tax return by a C corporation from the fifteenth day of the third month following the close of the taxable year (March 15 for calendar-year taxpayers) to the fifteenth day of the fourth month following the close of the taxable year (April 15 for calendar-year taxpayers).
Form 1120 (or Form 7004). This form is due on the 15th day of the 4th month after the end of the corporation’s tax year.
Generally, a corporation must file its income tax return by the 15th day of the 4th month after the end of its tax year.
the income tax return required under section 6012 of a domestic C corporation (as defined in section 1361(a)(2)) or of a foreign C corporation having an office or place of business in the United States shall be filed on or before the fifteenth day of the fourth month following the close of the taxable year.
Generally, a corporation must file its income tax return by the 15th day of the 4th month after the end of its tax year.
A corporate taxpayer is required to file an annual tax return (generally Form 1120) by the 15th day of the fourth month following the close of its tax year. … 15 April for C corporations, 15 March for S corporations (Form 7004 may be filed to obtain an automatic six-month extension).
In the case of returns under section 6012, 6013, or 6017 (relating to income tax under subtitle A), returns made on the basis of the calendar year shall be filed on or before the 15th day of April following the close of the calendar year and returns made on the basis of a fiscal year shall be filed on or before the 15th day of the fourth month following the close of the fiscal year, except as otherwise provided in the following subsections of this section.
§ 6072. Time for filing income tax returns (a) General rule In the case of returns under section 6012, 6013, or 6017 (relating to income tax under subtitle A), returns made on the basis of the calendar year shall be filed on or before the 15th day of April following the close of the calendar year and re turns made on the basis of a fiscal year shall be filed on or before the 15th day of the fourth month following the close of the fiscal year, ex cept as otherwise provided in the following sub sections of this section.
C corporations file by April 15. … April 15, 2026 - Taxes for C corporations are due. Businesses organized as a C corporation need to file Form 1120 by April 15, 2026, if they are a calendar year business.
For "regular" corporations (such as C corporations) that operate on a calendar year, their federal income tax return (Form 1120) for the 2025 tax year is due on April 15, 2026.
In the case of returns under section 6012, 6013, or 6017 (relating to income tax under subtitle A), returns made on the basis of the calendar year shall be filed on or before the 15th day of April following the close of the calendar year and returns made on the basis of a fiscal year shall be filed on or before the 15th day of the fourth month following the close of the fiscal year, except as otherwise provided in the following subsections of this section.
(a) General rule.--In the case of returns under section 6012, 6013, or 6017(relating to income tax under subtitle A), returns made on the basis of the calendar year shall be filed on or before the 15th day of April following the close of the calendar year and returns made on the basis of a fiscal year shall be filed on or before the 15th day of the fourth month following the close of the fiscal year, except as otherwise provided in the following subsections of this section.
(a) General rule. In the case of returns under section 6012, 6013, or 6017(relating to income tax under subtitle A), returns made on the basis of the calendar year shall be filed on or before the 15th day of April following the close of the calendar year and returns made on the basis of a fiscal year shall be filed on or before the 15th day of the fourth month following the close of the fiscal year, except as otherwise provided in the following subsections of this section.
the income tax return required under section 6012 of a domestic C corporation (as defined in section 1361(a)(2)) or of a foreign C corporation having an office or place of business in the United States shall be filed on or before the fifteenth day of the fourth month following the close of the taxable year.
The original federal due date for filing a calendar year C-corporation tax return (Form 1120) is the 15th day of the fourth month following the close of the corporation’s tax year. For a calendar year C-corporation, this means the return is due on April 15 of the following year.
returns made on the basis of the calendar year shall be filed on or before the 15th day of April following the close of the calendar year and returns made on the basis of a fiscal year shall be filed on or before the 15th day of the fourth month following the close of the fiscal year, except as otherwise provided in the following subsections of this section.
Form 1120 is due the 15th day of the 4th month after the corporation’s tax year ends, which is April 15 for calendar-year corporations, per the IRS.
1. Calendar Year Corporations: - Due Date: March 15th of the year following the tax year
For most C-corporations, the Internal Revenue Code (IRC) Section 6072(b) dictates a clear timeline: your tax return is due by the 15th day of the fourth month following the close of your tax year. … If your corporation operates on a standard calendar year (ending December 31), your filing deadline for the 2025 tax year is Wednesday, April 15, 2026.
When it comes to tax deadlines, C corps default to a calendar year. … | April 15, 2026 | Federal tax filing | Form 1120 |
If your corporation follows the calendar year (January 1 to December 31), your Form 1120 is due by April 15 of the following year.
April 15 (calendar year) or 15th day of 4th month after fiscal year end
Typically, it’s due on the 15th day of the 4th month after your tax year ends(for example, a calendar-year C-corp tax return for 2025 is due April 15, 2026).
Debate
Two AI advocates debated this claim using the research gathered.
Argument for
The claim is conclusively established by the primary legal text itself: 26 U.S.C. § 6072(a) (Sources 9, 10, 13, 14, 15, 18) explicitly states calendar-year income tax returns 'shall be filed on or before the 15th day of April,' and the implementing Treasury regulation 26 CFR 1.6072-2 (Sources 1, 6, 16) confirms this applies to domestic C corporations, with the Federal Register (Sources 2, 3) documenting the statutory amendment that fixed April 15 as the calendar-year C corporation due date since 2016. This statutory and regulatory foundation is unanimously corroborated by the IRS's own official publications (Sources 4, 5, 7), the PwC tax guide (Source 8), and numerous independent tax-industry sources (Sources 11, 12, 17, 19, 21, 22, 23, 24, 25), forming an overwhelming and virtually unbroken consensus across authoritative statute, regulation, and practitioner guidance that the claim is TRUE.
The Proponent selectively quotes the general rule in § 6072(a) while omitting its express qualification, "except as otherwise provided," and thus treats an ordinary deadline as an unconditional one (Sources 9 and 10). The controlling C-corporation regulation and current IRS guidance state the deadline as the fifteenth day of the fourth month after year-end, so repetition of the usual April 15 calendar-year result does not prove the motion's absolute wording (Sources 1 and 4).
Argument against
The claim improperly states an unconditional exact deadline: the governing rule is that a C-corporation return is due on or before the fifteenth day of the fourth month after year-end, not invariably “on April 15” (Source 1, ecfr.gov; Source 4, IRS). Even the statutory calendar-year language expressly operates subject to exceptions elsewhere in the section, so the brief supports April 15 as the ordinary rule rather than the motion's absolute claim (Source 9, U.S. Code).
The Opponent's own cited sources undercut the rebuttal: Source 9 explicitly states calendar-year returns 'shall be filed on or before the 15th day of April,' and the caveat 'except as otherwise provided in the following subsections' refers to specific corporate categories like cooperatives (Source 10), not a repudiation of the calendar-year default, so this is a fallacy of exception—treating a narrow carve-out as if it negates the general rule. The Opponent also mischaracterizes the '4th month' phrasing as a departure from April 15, when Sources 2, 3, 8, and 11 explicitly equate the two for calendar-year filers, meaning the 'fourth month' language and 'April 15' are not competing rules but the same rule stated in general and applied form.
Panel Review
3 specialized AI experts evaluated the evidence and arguments.
Reviewer 1 — The Logic Examiner
Sources 1 and 4 set the C-corporation deadline as the fifteenth day of the fourth month after year-end, which entails April 15 for a calendar-year corporation; Sources 2, 3, and 9 directly state that calendar-year C-corporation returns are due April 15. The opponent correctly notes that statutory exceptions and practical deadline adjustments can exist, but that does not defeat the claim as the ordinary legal due-date rule, so the claim is true under its natural reading.
Reviewer 2 — The Source Auditor
Authoritative government sources, including the U.S. Code (Source 9), the Federal Register (Sources 2 and 3), and IRS publications (Sources 4 and 5), consistently confirm that a calendar-year C corporation's federal income tax return is due on the 15th day of the fourth month following the close of the tax year, which is April 15. While one lower-quality blog (Source 20) incorrectly lists March 15, the overwhelming consensus of primary legal and regulatory texts supports the claim.
Reviewer 3 — The Precision Analyst
The claim's date, scope (calendar-year C corporation federal income tax return), and strength match the governing rule: statute, regulation, Federal Register, and IRS guidance (Sources 1–5, 8–12) all equate the fifteenth day of the fourth month after year-end with April 15 for calendar-year C corporations. Minor statutory exceptions for narrow categories do not falsify the ordinary due date as worded, so the claim is true at its stated strength.
Panel summary
Primary legal and regulatory sources establish that corporate income tax returns are generally due on the 15th day of the fourth month after the tax year closes. For a calendar-year C corporation, that date is April 15. IRS guidance and reputable secondary sources consistently support this reading. The logic correctly translates the statutory timing rule into the stated calendar date, while the claim's scope and date are precise. Narrow exceptions and weekend or legal-holiday adjustments do not materially alter the ordinary rule.