A calendar year runs January 1 through December 31. A fiscal year is any other 12 consecutive months ending on the last day of a month other than December. When people talk about fiscal year vs. calendar year for taxes, the practical question is which one you’re allowed to use, and the answer depends almost entirely on your entity type: individuals and sole proprietors are locked into the calendar; C corporations can pick freely; S corporations, partnerships, and personal service corporations default to the calendar and have to work for anything else.
What Each Term Actually Covers
The calendar year is the default. You’re required to use it if you keep no books, have no established accounting period, or if your current tax year doesn’t qualify as a fiscal year under the statute.1Internal Revenue Service. Tax Years
A fiscal year is any 12-month period ending on the last day of a month other than December.2Office of the Law Revision Counsel. 26 USC 441 – Period for Computation of Taxable Income A retailer might run February 1 through January 31; a government contractor might run July 1 through June 30. The point of picking a fiscal year is to close the books when the business’s own cycle is quiet, not at an arbitrary point in the middle of peak activity.
There’s a variant called a 52/53-week fiscal year. It always ends on the same weekday (say, the last Saturday in January), so the year is either 52 or 53 weeks long. It exists for businesses that plan around weekly cycles and is authorized by the same statute.2Office of the Law Revision Counsel. 26 USC 441 – Period for Computation of Taxable Income
Which Tax Year You’re Allowed to Use
The rules aren’t about preference. The IRS restricts each entity type to prevent owners from deferring income by mismatching the business’s year against their personal return.
Individuals and Sole Proprietors
If you file a personal return, you’re on a calendar year. A sole proprietor’s business income flows onto that same return, so the business year must match. Switching requires IRS approval, and in practice almost no individual does it.1Internal Revenue Service. Tax Years
C Corporations
C corporations have the widest latitude. They can adopt any fiscal year without proving a business purpose to the IRS.3Internal Revenue Service. Starting or Ending a Business A retail chain can pick a January 31 year-end so holiday sales and returns fall inside one period. A construction company can close after the building season. Because a C corp pays its own tax and doesn’t flow income through to owners, letting it pick a fiscal year doesn’t shift anyone else’s tax bill.
S Corporations and Personal Service Corporations
The default is the calendar year. The permitted alternatives are a year elected under Section 444, a 52/53-week year tied to the calendar year, or a fiscal year the entity can justify to the IRS as its natural business year.4Internal Revenue Service. Publication 538 – Accounting Periods and Methods The restriction exists because these entities pass income through to owners who file on the calendar year. Letting the business run on a different clock would let income slip between periods.
Partnerships
Partnerships follow a tiered rule to keep their year aligned with their partners’ years. First, the partnership uses the tax year of any partners who together hold more than half of the profits and capital. After a change to match this majority interest, there’s a two-year grace period before the partnership can be forced to change again.5Office of the Law Revision Counsel. 26 USC 706 – Taxable Years of Partner and Partnership
If no year commands a majority, the partnership uses the year shared by all its principal partners (those owning 5 percent or more). If the principal partners don’t share a year, the partnership defaults to whichever year produces the least aggregate deferral of income across all partners.5Office of the Law Revision Counsel. 26 USC 706 – Taxable Years of Partner and Partnership
Why a Business Might Want a Fiscal Year
The operational case comes down to matching the reporting window to reality. A retailer on a January 31 year-end captures the entire holiday season, including post-holiday returns and markdowns, inside one set of financial statements. Cutting the year off on December 31 splits that cycle in two.
Year-end work also lands somewhere manageable. Closing the books, preparing for audit, budgeting, and running performance reviews all compete for attention with daily operations. A resort company slammed in December has good reason to close its books in April.
How Your Tax Year Changes Your Deadlines
Every filing and payment deadline moves with your tax year. That’s the direct consequence of the choice.
Annual Returns
Partnerships and S corporations file by the 15th day of the third month after the year ends. For calendar-year filers, that’s March 15.6Internal Revenue Service. Publication 509 (2026) – Tax Calendars C corporations file by the 15th day of the fourth month after year-end, so April 15 for a calendar-year C corp.3Internal Revenue Service. Starting or Ending a Business One exception: C corporations with a June 30 year-end file by September 15 rather than October 15.
Change the year-end and the return date shifts. A partnership with a March 31 year-end owes its return by June 15. A C corporation on a September 30 year-end owes by January 15. K-1s to partners and shareholders move on the same schedule.
Estimated Tax Payments
Corporations pay estimated tax on the 15th day of the 4th, 6th, 9th, and 12th months of their tax year. Individuals on a fiscal year (rare, but permitted) pay on the 15th day of the 4th, 6th, and 9th months, and on the 15th day of the first month after year-end.6Internal Revenue Service. Publication 509 (2026) – Tax Calendars
This is the practical reason many small businesses stay on the calendar year even when they don’t have to. A calendar year for the business and a calendar year for the owner means one deadline schedule. A fiscal-year pass-through creates two calendars running in parallel.
Two Ways to Get a Fiscal Year You Weren’t Handed
S corporations, partnerships, and personal service corporations that would otherwise be stuck on the calendar year have two paths to something different.
The Section 444 Election
Section 444 lets these entities pick a fiscal year that defers income by no more than three months. If the required year is the calendar year, the elected year has to end no earlier than September 30.7United States Code. 26 USC 444 – Election of Taxable Year Other Than Required Taxable Year
The catch is that any deferral has to be paid for. The entity makes an annual required payment on Form 8752, calculated at a flat rate on the deferred income, which largely erases the tax benefit of the shift. The election itself is made on Form 8716, due by the earlier of the return due date (without extensions) for the elected year or the 15th day of the fifth month after that year begins.8Internal Revenue Service. Understanding Your CP287 Notice Section 444 gives you the calendar shift; it doesn’t give you a free deferral.
The Natural Business Year Test
If you can prove your requested year-end matches your actual business cycle, you can get a fiscal year without the Section 444 tradeoff. The standard is the 25 percent gross receipts test. Take the gross receipts from the last two months of your requested year-end, divide by the full 12 months’ receipts, and do this for each of the three most recent years. If the result is 25 percent or higher in all three years, that year-end is your natural business year.9Internal Revenue Service. Rev. Proc. 2002-38
Two things to know. If some other year-end produces an even higher three-year average, the IRS wants that one instead. And you need at least 47 months of gross receipts history to run the test, so a new business can’t use it.
Adopting or Changing Your Tax Year
A new business adopts its tax year simply by filing its first income tax return on that period. No separate form is required. Getting an EIN, filing an extension, or paying estimated tax doesn’t lock you in.10Internal Revenue Service. Publication 583 – Starting a Business and Keeping Records The entity-type restrictions still apply. A new partnership owned by calendar-year individuals can’t just file its first return on a June 30 year-end.
Changing an existing tax year is formal. Most changes go through Form 1128, and many qualify for automatic IRS approval if the entity hasn’t changed its year within the past 48 months.11Internal Revenue Service. Instructions for Form 1128 Changes that don’t qualify for automatic approval require a ruling request, with the application filed by the 15th day of the second calendar month following the close of the short period.12eCFR. 26 CFR 1.442-1
Any change creates a short tax year, the gap between the old year-end and the new one, which requires its own return. The IRS annualizes income on that short return so taxpayers can’t use a partial year to stay in lower brackets.13Office of the Law Revision Counsel. 26 USC 443 – Returns for a Period of Less Than 12 Months Missing the short-period return triggers the standard failure-to-file penalties, and for partnerships and S corporations those penalties run per partner or shareholder per month, which adds up quickly on a small firm.14Internal Revenue Service. Failure to File Penalty If you’re changing years, the short-period return is the thing not to overlook.