There are aspects of small business taxes that draw out many questions, one of the biggest is, “When are small business taxes due?”

Depending on how your business is structured, your tax deadline will either be March 15th or April 15th. While that bit of information might answer your most pressing question, there are still plenty of other variables that you should be aware of.

In the next few sections, you’ll learn about how business structure impacts small business tax deadlines, what you should know about estimated taxes, how to file a business tax extension and what happens if you should miss a tax deadline.

When Are Business Taxes Due?

Tax Day in the U.S. is always April 15th. However, that doesn’t mean your taxes are due on this exact date. If the 15th happens to fall on a weekend or holiday, the deadline moves to the following business day. For example, for Tax Year 2017, tax returns were due Tuesday, April 17th. The additional day was added because the District of Columbia observed Emancipation Day, which is a legal holiday in Washington, D.C.

For Tax Years 2018 and 2019, April 15th falls on a Monday and Wednesday, respectively, thanks to 2020 being a Leap Year.

Small Business Tax Deadlines By Structure

While April 15th is a date the majority of Americans need to be cognizant of, it’s a bit different for small business owners. The way your business organization is structured will impact how you’ll file small business taxes.

Here’s when each of the most popular business organizations are required to file:

Sole Proprietorships and Single-Member LLCs

Businesses structured as one of these two organizations are required to file Form 1040 Schedule C along with their personal tax return by April 15th.

Partnerships and Multi-Member LLCs

Businesses structured as one of these two organizations are required to file Form 1065 and Schedule K-1 from each owner by March 15th.


Companies filed as S-Corps are required to file Form 1120S and Schedule K-1 from each shareholder by March 15th.


Companies filed as C-Corps are required to file Form 1120 and Schedule K-1 from each shareholder by April 15th.

Estimated Tax Payments

As defined by the IRS, “estimated tax is the method used to pay tax on income that is not subject to withholding.” This income includes self-employment, dividends, rental, interest and capital gains. Estimated taxes are paid through quarterly installments throughout the year.

Who Needs to Pay Estimated Tax

Businesses that expect to owe taxes of $1,000 or greater at the time of their return are required to pay estimated taxes. The requirements for corporations are slightly different as they need to make estimated tax payments if they believe they will owe $500 or more in taxes. In addition, if your tax was more than zero in the prior year, you may have to pay estimated tax for the current year. For more details on who must pay estimated tax, consult the worksheet found in Form 1040-ES, Estimated Tax for Individuals (PDF), or Form 1120-W, Estimated Tax for Corporations (PDF).

How To Calculate Estimated Tax

To figure out how much you should pay in estimated tax, you need to first determine your expected adjusted gross income, taxable income, taxes, deductions and credits for the year.

Using the elements just described from the previous year’s income as a guide, use the worksheet found in Form 1040-ES to project your estimated tax. Your goal using this worksheet is to get an idea of the need to estimate the amount of income you expect to earn for the year.

Each quarter will present another opportunity to more accurately assess your income, meaning you will continue to use Form 1040-ES throughout the year. While it may be challenging, estimating your income as precisely as possible will allow you to avoid penalties and overpayment.

Corporations differ from other business organizations here as well, as they use Form 1120-W to figure estimated tax.

How Estimated Tax Is Divided

Each business maps out their plan for the year in quarters, which is the same way the IRS divides their payment periods. For example, for Tax Year 2018, these payments were due April 17, June 15, and Sept. 17, 2018, with final payment submitted on Jan. 15, 2019. For the current Tax Year 2019, estimated tax payments are as follows:

  • April 15, 2019
  • June 17, 2019
  • Sept. 16, 2019
  • Jan. 15, 2020

Paying Estimated Tax

The IRS allows payments to be remitted online, by phone or by mail. For more details, see the section of Form 1040-ES titled “How to Pay Estimated Tax,” as well as Publication 505, Tax Withholding and Estimated Tax.

The Electronic Federal Tax Payment System (EFTPS) is arguably the easiest and most convenient way for businesses to pay federal taxes, allowing organizations to pay federal tax deposits (FTDs), installment agreement and estimated tax payments.

Installments can be made in weekly, bi-weekly or monthly increments, so long as the total tax bill is satisfied at the end of the quarter. Much like a digital bank statement, the EFTPS also allows you to review historical payments to review what you’ve already paid and how much remains.

If your business is structured as a corporation, you are required to use the Electronic Federal Tax Payment System. To learn more about this requirement, see Publication 542, Corporations.

How to File a Business Tax Extension

Running your own business is quite involved, meaning that things sometimes get put on the backburner even when they’re quite important. If, for whatever reason, you’re unable to meet the deadlines set out for your specific business organization, you’re able to file for an extension.

A business tax extension allows you to file your tax returns a little later, though it behooves you to pay as much as possible to avoid penalties and interest fees (penalties for late payments are calculated at 0.5 percent of the unpaid tax balance per month, with 25 percent being the maximum).

Sole Proprietorships and Single-Member LLCs

Sole proprietorships and single-member LLC tax extension filings give business owners until October 15 to submit their taxes.

Partnerships and Multi-Member LLCs

Partnerships and multiple-member LLCs tax extension filings give business owners until September 15 to submit their taxes.


S-corporations tax extension filings give business owners until September 15 to submit their taxes.


C-corporations tax extension filings give business owners until October 15 to submit their taxes.

What Happens If You Miss a Business Tax Deadline?

While it’s not the end of the world, missing a tax deadline can add additional financial burden to your business. If you do miss a deadline, the IRS recommends that you file and pay as soon as possible. Oftentimes, a moderate financial penalty is assessed to your tax account, though as long as the taxes are satisfied, you will not be subject to any other fees for missing a deadline.

Payments can be made to the IRS by mail, as well as IRS Direct Pay, which is the fastest method to settle your tax balance. Filing by the national deadline, October 15th, will be the best way to avoid further penalties.


Small business taxes require careful review and attention to detail. While the tax code is full of cumbersome language and a litany of loopholes, the basics of business taxes are straightforward, especially when it comes to deadlines. The best way for you to stay in the good graces of the IRS is to pay on time and to have all of your details arranged properly.

If you’re concerned that you may miss a deadline or you’re not sure your business will have everything you need to file, talk with your CPA to secure all of the documents, details and payment specifics you need.