A U.S. company incorporated in August: which year-end should it pick, and when is the first Form 1120 due?

Direct answer: The tax year is adopted by the first Form 1120. If nothing has been filed, the choice is open; an August incorporation can pick a July 31 year-end and file its first return by November 15 of the following year, provided the books are kept on that fiscal year.

Every autumn the same question arrives: "We incorporated last August and have never filed a tax return. Are we already late?" The answer turns on something most owners have not been told: a U.S. corporation's tax year is not set on the day of incorporation, and it is not set by the month written on the EIN application. It is adopted by the first income tax return the company files. No return yet means no tax year yet, and no tax year means no deadline yet. This article walks through the rule, its limits, and a date table you can read straight off.

1. When a tax year becomes fixed

Treasury Regulation §1.441-1(c)(1) is explicit: a new taxpayer adopts a tax year by filing its first federal income tax return using that tax year. IRS Publication 538 lists three things that do not constitute adoption: filing an application for an extension (Form 7004), applying for an employer identification number (Form SS-4), and paying estimated taxes. The "closing month of accounting year" on line 12 of the SS-4 is registration information, not a commitment. Many founders type "December" there and assume the matter is closed. It is not.

The reverse is also true. Once the first Form 1120 has been filed on a given year, that year is adopted. Changing it later requires Form 1128, Application to Adopt, Change or Retain a Tax Year; most C corporations that meet the conditions can use an automatic approval procedure, but it is a separate process with its own tests, not a matter of editing a date. The year used on the first return deserves one deliberate decision before filing rather than regret afterwards.

• The tax year is adopted by the first Form 1120 (Reg. §1.441-1(c)(1))
• SS-4, Form 7004 and estimated payments do not adopt a year (Pub. 538)
• After the first return, a change requires Form 1128
• A company that has never filed still has the choice open, and the deadline with it

2. Three limits: no books means calendar year

"Still open" does not mean "anything goes." The first limit is IRC §441(g): if the taxpayer keeps no books, has no annual accounting period, or has one that does not qualify as a fiscal year, its tax year is the calendar year. The second is Reg. §1.441-1(b)(5)(ii): a fiscal year is recognized only if the taxpayer's books are kept in accordance with that fiscal year. Together they mean that a July 31 year-end is available only if the company actually closes its books on July 31, with a trial balance, income statement and balance sheet cut off on that date. A company that has done no bookkeeping since incorporation must first build the books and close them on the chosen fiscal year; otherwise the IRS sees a calendar-year taxpayer by default.

The third limit is entity type. Partnerships, S corporations and personal service corporations have "required tax years" that generally force the calendar year or the owners' year. A C corporation owned by Chinese shareholders is not subject to those rules and may choose any month-end. A single-member LLC owned by a Chinese individual, however, does not file Form 1120 at all; its income flows onto the owner's return and follows the owner's year, so there is nothing to choose.

• No books or no accounting period → calendar year is mandatory (§441(g))
• A fiscal year is recognized only if the books are kept on it (Reg. §1.441-1(b)(5)(ii))
• C corporations may choose any month-end; partnerships, S corporations and PSCs are constrained
• Close the books on the intended year-end first, then decide

3. When the first return is due: 15th day of the 4th month, with a June 30 exception

The general rule for Form 1120 is the 15th day of the 4th month after the end of the tax year. A corporation with a June 30 year-end is the exception and must file by the 15th day of the 3rd month, September 15. A new corporation's first year is usually a short period of less than 12 months; a short-period return follows the same 4th-month rule, and a short year ending anytime in June is treated as ending June 30. Form 7004 gives an automatic six-month extension (June 30 year-ends beginning before 2026 had seven months; for tax years beginning in 2026 it is six). The extension covers filing, not payment.

For Chinese-owned companies the form that matters more is Form 5472. A U.S. corporation that is 25% or more foreign-owned files one Form 5472 per related party, attached to Form 1120 and due on the same date including extensions. If the 1120 shows no tax, the late-filing penalty on the 1120 itself is small; Form 5472 is different. Each form not filed, or filed "substantially incomplete," carries a penalty starting at $25,000, and if the failure continues more than 90 days after IRS notice, another $25,000 accrues per related party for each 30-day period. The year-end decision is, in practice, the decision about when the 5472s are due.

• General rule: 15th day of the 4th month after year-end (next business day if a weekend or holiday)
• June 30 year-end: 15th day of the 3rd month
• Short periods follow the same rule; Form 7004 adds six months for filing only
• Form 5472 is due with the 1120, $25,000 and up per form

4. August incorporation: only July 31 pushes the first return to November 15

Apply those rules to a C corporation incorporated on August 10, 2026 that has not yet filed anything. A tax year cannot exceed 12 months, so the latest possible first year-end is July 31, 2027, the month-end before the incorporation month. Each month earlier moves the deadline a month earlier; June 30 runs into the 3rd-month rule and lands on the same September 15 as a May 31 year-end.

The same logic works for any incorporation month: the latest permissible year-end is always the month-end before the incorporation month, and the first return is due on the 15th day of the 3rd month after the incorporation month in the following year. A July incorporation is capped by the June 30 rule at September 15.

An anonymized example: a U.S. C corporation wholly owned by a Chinese shareholder, incorporated in August 2025, with two related parties, a first-year loss and very little activity, had filed nothing by autumn 2026. On a calendar-year view its 2025 Form 1120 and two Forms 5472 were due April 15, 2026, and the exposure was two 5472 penalties starting at $50,000 combined. But because it had never filed, no tax year had been adopted. Closing the books for August 2025 through July 2026 and filing the first Form 1120 on a July 31 year-end makes the due date November 15, 2026, still open. That is not a trick; it is what the regulation says, provided the books are actually kept on that fiscal year.

• Latest year-end = the month-end before the incorporation month; anything later exceeds 12 months
• August incorporation → July 31 year-end → due November 15 of the following year
• July incorporations are capped by the June 30 rule at September 15
• A company that has never filed should close the books on the intended fiscal year before filing the first return

5. Four calendar-based items to check before choosing

Pushing the first return to the latest possible date is not always the best answer. First, parent consolidation: a Chinese parent reports on the calendar year, so a subsidiary on a July 31 fiscal year needs a second December 31 cut-off every year for group reporting. Second, the states: most state income tax years follow the federal year, but Delaware's annual report and franchise tax, and most states' annual reports, fall on calendar dates regardless of the tax year; a fiscal year does not defer them. Third, information returns: Forms W-2, 1099 and 1042-S are always calendar-year and are due by the end of January whatever the company's tax year. Fourth, sales tax and payroll tax periods run on calendar months or quarters, independent of the income tax year.

For most Chinese-owned subsidiaries that plan to operate long term and consolidate upward, December 31 remains the sensible default. A fiscal year suits companies with a pronounced seasonal cycle, or a first year in which the books need time to be put in order. Whichever year is chosen, confirm three things before the first 1120 goes out: the bookkeeping period matches the year-end, a Form 5472 is ready for every related party, and any extension is filed before the original due date.

• A calendar-year parent means an extra cut-off for a fiscal-year subsidiary
• State annual reports and franchise taxes fall on calendar dates, independent of the tax year
• W-2, 1099, 1042-S, sales tax and payroll tax all run on the calendar
• Long-term operation with consolidation: December 31 is usually simpler; books that need time: a fiscal year can buy months