Tax Year
The 12-month accounting period for calculating and filing taxes. For most individuals, the tax year is the calendar year (January 1 through December 31).
A tax year is the annual period covered by a tax return. Most individual taxpayers and many businesses use the calendar year — January 1 through December 31. Some businesses may choose a fiscal year that ends on the last day of a month other than December, but individuals almost always use the calendar year.
Your tax year determines when income is reported and when deductions are taken. Under the cash method of accounting (used by most individuals), income is reported when received and expenses are deducted when paid. Under the accrual method (used by some businesses), income is reported when earned and expenses when incurred, regardless of when cash changes hands.
Tax returns for a calendar year are due on April 15 of the following year (or the next business day if April 15 falls on a weekend or holiday). For example, your 2025 tax year return covers income earned from January 1 to December 31, 2025, and is due April 15, 2026.
How it works
A tax year is the 12-month period your return covers, and for almost every individual taxpayer that is the calendar year — January 1 through December 31. The tax year determines the window in which your income, deductions, and life events, such as a marriage, a home sale, or a job change, get reported, even if the actual filing and payment happen months later.
You encounter your tax year implicitly on nearly every form you touch — your W-2 and 1099s report income for a specific calendar year, your Form 1040 is labeled for that year, and the standard deduction, tax brackets, and contribution limits that apply are all pinned to that same year rather than the year you actually file or pay.
The accounting method matters here too: most individuals use the cash method, reporting income when received and deducting expenses when paid, so a paycheck deposited on December 31 counts in that tax year even if the pay period technically extended into January. A less common source of confusion is that a tax year and a filing season are not the same thing — a 2025 tax year return is filed in the 2026 filing season, and people sometimes call the filing season year the tax year by mistake.
Example: which tax year a payment belongs to
A freelancer invoices a client in December 2025 but does not actually receive payment until January 3, 2026, because the client pays late.
Under the cash method used by most individuals, that income belongs to the 2026 tax year — the year it was actually received — not 2025, even though the work was performed and invoiced the year before.
Frequently asked questions
Is the tax year the same as the calendar year?
Which tax year does my income belong to if I get paid late?
Why do people say 2025 tax year but file in 2026?
Related Terms
Fiscal Year
A 12-month accounting period that ends on the last day of any month other than December. Used mainly by businesses and some trusts, not by individual taxpayers.
Tax Return
The form(s) you file with the IRS to report income, claim deductions and credits, and calculate your tax liability or refund. For individuals, this is Form 1040.
Extension
A request to push your tax return filing deadline from April 15 to October 15. An extension gives more time to file but not more time to pay any taxes owed.