Business tax return deadlines by entity type

Every business owner eventually faces the same question at year end: which return do we file, and when is it due?

The answer depends mostly on how the business is taxed. This guide covers federal income tax deadlines for calendar-year businesses. It is general information, and state deadlines can differ.

What is a tax year?

A tax year is the annual period the business uses to measure its income. Most small businesses use the calendar year, January 1 through December 31.

Some businesses use a fiscal year that ends on the last day of a month other than December. Partnerships, S corporations and personal service corporations face limits on choosing a fiscal year, and changing a tax year generally requires IRS approval.

When is each return due?

For calendar-year businesses, partnerships file Form 1065 and S corporations file Form 1120-S by March 15. C corporations file Form 1120 by April 15. Sole proprietors and single-member LLCs that have not elected corporate treatment report business income on Schedule C with their Form 1040, also due April 15.

Fiscal-year businesses count from the end of their year. Partnerships and S corporations generally file by the 15th day of the third month after year end, and C corporations by the 15th day of the fourth month. When a due date falls on a weekend or legal holiday, it moves to the next business day.

How do extensions work?

Businesses request an automatic extension with Form 7004, which generally gives 6 more months to file. Individuals, including sole proprietors, use Form 4868.

An extension to file is not an extension to pay. Tax owed is still due on the original date, and interest and penalties can apply to anything paid late. If you need help pulling the numbers together before the deadline, see our tax preparation service.

How do estimated payments fit in?

C corporations that expect to owe tax generally pay it in four estimated installments, due on the 15th day of the 4th, 6th, 9th and 12th months of the tax year. Those payments are credited against the tax shown on the annual return.

Owners of pass-through businesses usually make estimated payments on their individual returns instead. Our guide on quarterly estimated taxes explains the due dates and the safe harbor rules.

What if the business has a loss?

A corporation generally files every year it exists, even with no income or a loss. Filing also records the loss so it can be used later.

Under current federal law, net operating losses arising in tax years after 2017 are generally carried forward rather than back, and the deduction in a later year is limited to a portion of taxable income. If you are still deciding how the business should be taxed, the sole proprietorship, LLC or S corp guide compares the options. Check current IRS guidance and talk with your CPA about your own situation.