Business Tax Due Dates: Key Deadlines and Extensions

Know the Business Tax Due Date First

Most businesses file tax returns by the 15th day of the third or fourth month after the tax year ends. The exact business tax due date depends on the business structure and tax year.

Partnerships and S corporations usually file by March 15 when they use a calendar year. C corporations usually file by April 15. These dates apply to common calendar-year filers in the United States.

Your business may have other dates for estimated tax payments, payroll taxes, or state returns. This guide covers federal income tax returns. Check each deadline before you send a return or payment.

For the latest federal dates, use the IRS tax calendar guidance. It explains filing dates, payment dates, and holiday shifts.

Key Deadlines by Business Structure

Your business structure plays a major role in the filing schedule. The table below shows the usual federal dates for calendar-year businesses.

Business type	Common federal form	Usual calendar-year due date
Partnership	Form 1065	March 15
S corporation	Form 1120-S	March 15
C corporation	Form 1120	April 15
Sole proprietor	Schedule C with Form 1040	April 15

A partnership or S corporation return is due on the 15th day of the third month after year-end. A C corporation return is usually due on the 15th day of the fourth month.

A sole proprietor reports business income on a personal return. That return normally follows the April 15 individual filing date. A single-member limited liability company often uses the same approach unless it chooses another tax status.

These dates can change when a business uses a short tax year or a special year-end. The return type also matters. Keep your structure and tax year clear before setting reminders.

Why Your Tax Year Changes the Date

Many small businesses use the calendar year. Their tax year ends on December 31. Their standard federal filing date then falls in March or April of the next year.

Some businesses use a fiscal year instead. A fiscal year ends on a date other than December 31. The business tax due date then moves with that year-end.

For example, assume a partnership ends its tax year on June 30. Its return is generally due on September 15. A C corporation with the same year-end is generally due on October 15.

Do not rely on a search for “business tax due date 2024” without checking the tax year. A date for a 2024 calendar-year return may fall in 2025. The filing year and the tax year are not always the same.

• Find the final day of the business tax year
• Count to the 15th day of the third or fourth month
• Confirm the rule for your return type
• Check for a weekend, holiday, or disaster relief change

Weekends, Holidays, and Disaster Relief

A deadline does not always stay on the date printed on a tax calendar. If the due date falls on a Saturday, Sunday, or federal holiday, the deadline moves to the next business day.

For example, a return due on Sunday is not late when filed on Monday. If Monday is a federal holiday, the deadline moves again. The IRS uses this rule for many federal filing and payment dates.

Natural disasters can create a longer filing window. The IRS may give affected businesses extra time to file returns and pay taxes. The relief area and covered dates depend on the specific disaster notice.

Check the IRS disaster relief page when a storm, wildfire, flood, or other event affects your records. Save proof of the event and keep copies of any relief notice tied to your area.

Extensions and the Forms You Need

A business can often request more time to file. An extension gives more time for the return. It does not usually give more time to pay the tax.

Partnerships and S corporations generally request an extension with Form 7004. The form is due by the original return deadline. An approved extension often gives six more months to file.

C corporations also use Form 7004 to request an extension. Form 1120 is the C corporation income tax return. It is not the extension form.

That distinction matters. Sending Form 1120 does not request extra time. Use the form that matches the action you need.

1. Estimate the tax owed before the original due date
2. Pay as much as the business can safely pay
3. Submit Form 7004 by the original filing deadline
4. File the full return by the extended date

An extension does not remove interest on unpaid tax. It may also not remove every penalty. A timely payment remains the best way to limit added cost.

What Happens When a Business Files Late?

Missing a filing deadline can lead to penalties and interest. The amount depends on the return, tax due, payment history, and length of the delay.

A late filing penalty may apply even when the business owes little tax. Partnerships and S corporations can face penalties for late returns. The penalty may apply for each month or part of a month late.

Unpaid tax can also gain interest from the payment due date. A filing extension does not stop that interest. The balance can grow while the return remains unfinished.

Act quickly after a missed deadline. File the return, pay what you can, and review penalty relief options. The IRS may waive some penalties when reasonable cause supports the request.

Do not ignore an IRS notice. Compare the notice with your records. Then ask a tax professional about the best response if the amount looks wrong.

Simple Ways to Stay on Track

Start with one master tax calendar. Add federal returns, state returns, payroll filings, estimated tax payments, and extension dates. Use separate alerts for preparation and final submission.

Set the first alert at least 60 days before the due date. Set a second alert 30 days before. Add a final check seven days before filing.

Keep clean records throughout the year. Store income reports, expense receipts, payroll data, asset details, and prior returns in one secure system. Good records make filing faster and reduce errors.

Review estimated tax payments each quarter. A business can owe a balance even when it files on time. Paying during the year may help avoid underpayment penalties.

Use this short check before each filing:

• Confirm the business structure and tax year
• Match the return to the right federal form
• Check the due date against the IRS calendar
• Look for weekend, holiday, or disaster changes
• Submit any extension before the original deadline
• Pay the expected balance by the payment deadline
• Save the filing receipt and payment record

A Practical Deadline Plan

The right business tax date starts with your year-end. Next, identify the return form and count to the correct month. Then check for special shifts and disaster notices.

For many calendar-year businesses, March 15 is the key date for partnership and S corporation returns. April 15 is the key date for C corporation and sole proprietor returns.

Those dates are common, not universal. Fiscal years, short years, elections, and special IRS relief can change them. Confirm the date before each filing season.

When a deadline is close, file an extension and pay an honest estimate. When a deadline has passed, file and pay without delay. Fast action can limit the cost of a mistake.