When are Business Taxes Due? | 2021 Fall Tax Deadlines

when are business taxes due?

While Tax Day is the only date most people may have circled on their calendar, there are many important business tax deadlines throughout the year. So to help your customers, we've developed an outline of everything you need to know to find out the answer to "when are business taxes due?"

The business tax due dates you’ll need to depend on your earnings as well as business structure; for example, if you’re a single-member LLC, you might be penciling in different tax deadlines than an S corporation owner.

When are business taxes due in 2021 (for the 2020 tax year)?

Many small or mid-size business owners ask questions like, “When are S corporation taxes due?” And “When are LLC taxes due?” If your business is an LLC, you might file as a sole proprietor, partnership, or corporation, depending on your business structure and even the corporation and partnership tax return due dates.

We outline the details of these familiar business entities and their tax filing due dates below. But, if you’re thinking you don’t have the time to meet fall tax deadlines always look to work with your tax accountant to request an extension.

August, & September business tax deadlines


September 15:  The third estimated quarterly tax payment for 2021 is due on this date.

September 15 : Extended deadline for calendar-year partnerships and multiple-member LLCs who file Form 1065 for their business. It’s also the S corporation business tax extension deadline (for the business’ return, not the owners). So if your business files a calendar-year Form 1120-S and filed an extension this year, you should file by September 15.

October, November, & December business tax deadlines


October 15:  This the due date for sole proprietors, single-member LLCs, S corporation owners, partner, and corporations with a tax extension.


December 1:  Consider making year-end tax moves to optimize your tax outcome. While Dec. 1 isn’t an official deadline, noting the date on your calendar can give you a nudge to explore your options before the year is out.

December 15:  The fourth estimated quarterly tax payment for corporations for 2021 is due on this date. Please note the fourth quarter payment is due at different times for individuals and corporations.


Prevent surprise tax bills by talking to your tax preparer before the end of the year. I’d recommend around mid-November. Share with them how your business (and personal finances if you own a pass-through entity) is tracking so they can give you actionable advice before 12/31.

The most common disappointment we hear from customers is a shocking tax bill. Be prepared and work with your tax professional in advance. Ask for the time to talk, don’t wait for them to reach out.

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