A tax year is the 12-month period used to report income, expenses, deductions, credits, and tax liability to the IRS. The tax year determines which income belongs on a tax return and when that return must be filed.
For most individuals, the tax year follows the calendar year, meaning income earned during one calendar year is reported on the tax return for that same year.
Types of Tax Years
Calendar Year
The calendar year is the most common tax year and is used by most individual taxpayers.
A calendar tax year:
- Begins on January 1
- Ends on December 31
- Includes all income earned during that period
For example, income earned between January 1, 2026, and December 31, 2026, is reported on a 2026 tax return, which is generally filed in 2027.
Fiscal Year
A fiscal year is a 12-month period that ends on the last day of any month other than December.
Fiscal years are commonly used by:
- Businesses
- Partnerships
- Estates
- Trusts
- Certain nonprofit organizations
A fiscal year may better align with an organization's business cycle or accounting practices. In many cases, IRS approval is required to change from a calendar year to a fiscal year.
Why the Tax Year Matters
Your tax year affects several important parts of the tax filing process.
It determines:
- Which income must be reported on your return
- Which deductions and credits can be claimed
- The deadlines for filing returns and extensions
- The tax laws and rates that apply
- Tax planning opportunities related to the timing of income and expenses
Using the correct tax year ensures your return accurately reflects your financial activity during the reporting period.
What Income Belongs in a Tax Year?
Generally, income is reported in the tax year it is received.
Examples include:
- Wages reported on Form W-2
- Interest reported on Form 1099-INT
- Dividend income reported on Form 1099-DIV
- Retirement distributions reported on Form 1099-R
- Self-employment income received during the year
For cash-basis taxpayers, which includes most individuals, income is typically taxable when it is actually or constructively received.
Example of a Tax Year
Suppose you earned:
- Wages from January 2026 through December 2026
- Interest income credited to your bank account during 2026
- Dividend income paid during 2026
All of this income would generally be reported on your 2026 federal income tax return.
That return is typically due by April 15, 2027, unless an extension is requested.
Tax Year vs. Filing Year
Many taxpayers confuse the tax year with the year they file their return.
The tax year refers to the year in which the income was earned.
The filing year refers to the year the tax return is submitted.
For example:
- Tax Year: 2026
- Filing Year: 2027
If you're filing a return in 2027 for income earned during 2026, you're filing a 2026 tax return.
Changing a Tax Year
Most individual taxpayers use the calendar year and generally do not have a choice of tax year.
However, certain businesses and organizations may adopt a fiscal year if they meet IRS requirements. Changing a tax year often requires filing specific IRS forms and obtaining approval.
How Tax Software Uses the Tax Year
When preparing a return, tax software uses the selected tax year to:
- Apply the correct tax laws and rates
- Determine eligible deductions and credits
- Import information from tax forms issued for that year
- Calculate filing deadlines and extension dates
Selecting the correct tax year is essential because tax rules can change from one year to the next.