Fiscal Year: Definition and How It Works

A fiscal year is any 12-month accounting period — or, under the 52/53-week year option in IRC §441(f), a period ending on the same day of the week each year — that does not end on December 31. A business or taxpayer that ends its year on December 31 is on the calendar year; one that ends on any other month-end (e.g., June 30, September 30) is on a fiscal year. The Internal Revenue Code uses the term "taxable year" interchangeably; IRC §441(a) requires every taxpayer to compute taxable income on the basis of their annual accounting period. The fiscal year a business adopts determines its tax return due dates, estimated tax payment schedule, and — for pass-through entities — the timing of income that flows to owners' individual returns.

IRC §441: The Governing Framework

IRC §441 establishes the basic rules for taxable year selection:

• Calendar year: A 12-month period ending December 31, required for taxpayers who keep no books, have no annual accounting period, or whose annual period does not qualify as a fiscal year.
• Fiscal year: A 12-month period ending on the last day of any month other than December (e.g., March 31 means the fiscal year runs April 1–March 31).
• 52/53-week year: Under IRC §441(f), a business may elect a year that ends on the same weekday (e.g., the last Saturday of September) each year, even if that date falls in a different calendar month in some years. The IRS treats this as a fiscal year for most purposes.

The IRS requires taxpayers to receive approval to change their taxable year on Form 1128, Application to Adopt, Change, or Retain a Tax Year, except in certain automatic-approval situations described in Revenue Procedure 2006-45.

Required Year Rules for Pass-Through Entities

C-Corporations generally may adopt any fiscal year they choose without restriction. Pass-through entities face mandatory taxable year rules:

S-Corporations (IRC §1378): Must use a calendar year unless the entity can demonstrate a "business purpose" (approved by the IRS under Rev. Proc. 2002-39) or makes a §444 election. See the S-Corporation glossary entry for full S-Corp background.

Partnerships and LLCs taxed as partnerships (IRC §706): Must use the taxable year of the partner or partners owning a majority interest (the "majority interest taxable year"), or if no majority, the taxable year of all principal partners, or if no common year exists, the calendar year — unless a business purpose or §444 election applies.

Sole proprietors: Report on Schedule C of Form 1040 and are bound to the individual's calendar year.

The practical effect of these rules is that most S-Corps, partnerships, and LLC pass-throughs operate on a calendar year.

The §444 Election and §7519 Required Payments

IRC §444 allows qualifying partnerships and S-Corporations to elect a fiscal year that results in a "deferral period" of no more than three months — meaning they can end their year on September 30, October 31, or November 30, even though their principal partners or shareholders are on a calendar year. The election is made on Form 8716, Election to Have a Tax Year Other Than a Required Tax Year.

The tradeoff: the entity must make annual required payments under IRC §7519 — essentially an interest-free deposit to the IRS equal to the tax on the income deferred by the fiscal year. These payments are due by May 15 each year and are reconciled on Form 8752. The §444 election is rarely made in practice because the §7519 cost often offsets any deferral benefit.

Effect on Tax Return Due Dates

A fiscal year changes every filing deadline. For most entity types, returns are due on the 15th day of the 3rd month after the fiscal year ends for pass-throughs, and the 15th day of the 4th month for C-Corporations:

See Business Tax Return Deadlines 2025 for the calendar-year deadlines and extension mechanics, and How to File a Business Tax Extension for Form 7004 procedures that apply to fiscal-year filers in the same way.

Estimated quarterly tax payments for fiscal-year C-Corps are also shifted: payments are due on the 15th day of the 4th, 6th, 9th, and 12th months of the fiscal year. See Quarterly Estimated Taxes for the underlying safe harbor math.

How CPAs Use Fiscal Year Planning

C-Corp income deferral: A C-Corp on a fiscal year ending January 31 can legitimately defer recognizing revenue until February, pushing it into the next taxable year. CPAs sometimes advise new C-Corps to adopt a fiscal year that aligns with a natural lull in the business cycle to compress the first short year and smooth multi-year tax liability.

Natural business year: The IRS recognizes a "natural business year" as a valid business purpose for a fiscal year election when 25% or more of the entity's annual gross receipts fall in the final two months of the proposed year (the "25% gross receipts test" in Rev. Proc. 2002-39). Retailers often qualify for a January 31 fiscal year; ski resorts may qualify for a March 31 year.

Accounting method interaction: The taxable year interacts with the accounting method. An accrual-basis taxpayer recognizes income when earned and expenses when incurred within each fiscal year — so choosing the right year end determines which transactions fall into which return. See Switching from Cash Basis to Accrual Accounting for the full §481(a) adjustment analysis when methods change.

Related Terms

• C-Corporation — entity most free to adopt a fiscal year without restriction
• S-Corporation — generally required to use calendar year under IRC §1378
• Check-the-Box Election — determines entity classification, which in turn governs the taxable year rules that apply