Key Takeaways

  • C corporation taxes are generally due by the 15th day of the 4th month after the end of the fiscal year (typically April 15 for calendar year-end).
  • For C corps with a fiscal year ending June 30, the deadline remains September 15 until 2025.
  • Late filings incur both penalties and interest charges.
  • Estimated taxes must be paid quarterly using IRS Form 1120-W.
  • State filing deadlines may differ from federal deadlines and should be verified.
  • Tax filing extensions (Form 7004) provide more time to file but not more time to pay taxes due.

The C corp tax return due date has been updated effective for the 2016 tax year, filed in 2017. The new deadline for filing Form 1120 for corporate taxes depends on the fiscal (tax) year of the corporation. 

Information on Tax Return Due Dates

  • If the fiscal year-end for the corporation is December 31, the new deadline for filing the 2017 return is April 17, 2018, on a yearly basis. For corporations that do not have December 31 as their year-end, the filing date will fall after the year-end on the 15th day of the 4th month.
  • If the due date for filing taxes fall on a holiday or the weekend, the date for filing moves to the first workday. For example, if the due date falls on Sunday, the new due date will be the following day; Monday.
  • An exception to the "day following due date" is upcoming in 2018. April 15 falls on Sunday and Monday, April 16 is a holiday in the District of Columbia. In this case, the due date will be the following day, Tuesday, April 17.
  • If your C corporation was started in 2017, you need to know the actual date the company began operating the business. You will not be allowed to deduct costs incurred prior to starting the business. It is best to consult with a tax professional about what items are deductible and those that are not. 

Quarterly Estimated Tax Payments

In addition to the annual tax return, C corporations must pay estimated taxes throughout the year if they expect to owe tax of $500 or more. These payments are generally due on the 15th day of April, June, September, and December. Form 1120-W is used to calculate estimated tax obligations. Failing to pay estimated taxes on time may result in underpayment penalties, even if the corporation pays the full tax owed by the return due date.

Tax Regulations for 2018

Fiscal year tax filers have different file dates and extension times.  For example, S corporations and partnerships have a due date to file tax returns on the 15th day of the third month that follows the end of their tax year. C corporations have a due date of the 15th day of the fourth month from the end of their tax year. A special rule is in effect for C corporations whose fiscal year has an end date on June 30. For these corporations, the date is deferred to December 31, 2025.

Companies filing Form 1065 - U.S. Return of Partnership income - have a maximum six-month extension period with the extended due date on September 15, the same as former years. Estates and Trusts filing Form 1041 have an increased extension time to five and a half months while Foreign Bank and Financial Accounts (FBAR) have been extended to six months. The filing due date is the same for an individual filing a Form 1040 so the FBAR so that the two are aligned for reporting purposes.

Individual states may not be the same as Federal filing dates. Verify when tax returns are due in your state. 

Penalties for Late Filing and Payment

If a C corporation fails to file its tax return on time, the IRS imposes a penalty of 5% of the unpaid taxes for each month or part of a month that the return is late, up to a maximum of 25%. If the payment is late, there’s an additional penalty of 0.5% of the unpaid taxes per month. Interest also accrues on any unpaid tax starting from the due date until the amount is paid in full.

Filing an Extension

Requesting an extension to file income tax is part of the business world. There are many steps to in getting the company books in order in preparation for tax time. 

It is recommended to request an extension versus rushing to put things in order and taking the chance of missing important information and filing an inaccurate return. An extension allows time for you and your certified public accountant (CPA) to do things correctly from the start. A positive way to look at the use of an extension is as a lifeline that will prevent your company from incurring penalties and interest because of missing or inaccurate information because you filed without being prepared.

C corporations, partnerships, and S corporations can request an extension by filing Form 7004. Individuals requesting an extension use Form 4868. Exempt organizations for charities and nonprofits can request a three-month extension by filing Form 4868. Requesting an extension to file a tax return does not extend the time for paying any tax liability that is due. Consult with a tax professional if you need to extend your filing date and make sure to pay any tax liability owed on time. 

How to File for an Extension

To request an automatic extension for filing a C corp tax return, file IRS Form 7004 by the original due date of the return. This grants a six-month extension, typically moving the due date from April 15 to October 15 for calendar-year corporations. However, the extension only applies to filing, not payment—any taxes owed must be paid by the original deadline to avoid penalties and interest. The IRS recommends submitting the extension electronically to ensure timely processing.

C Corporations and Foreign Entities

  • While you may be dealing with the stress of tax season and U.S. based corporations, the process can become more involved when you have business with foreign entities.
  • Companies with non-resident or non-citizen U.S. shareholders who own over 25 percent must file Form 5472.
  • Failure to file a correct Form 5472, to complete Form 5472, or for filing the form late along with the company's income tax return can result in a $10,000 penalty. The penalty is per shareholder per period.

State Tax Return Deadlines for C Corporations

While the federal tax deadline is consistent nationwide, state corporate tax deadlines can vary significantly. For example, California C corps must file by the 15th day of the 4th month after the end of the fiscal year (similar to the federal deadline), but some states use different timelines. It is important to consult the specific state’s department of revenue or a tax professional to determine local compliance requirements.

Frequently Asked Questions

1. When are C corp taxes due each year? C corp taxes are due by the 15th day of the 4th month after the end of the fiscal year. For most corporations using a calendar year, this falls on April 15.

2. Do C corporations need to pay quarterly taxes? Yes, if a C corp expects to owe $500 or more in tax, it must make quarterly estimated tax payments using IRS Form 1120-W.

3. What happens if a C corporation misses the tax deadline? The IRS imposes penalties for both late filing and late payment, along with accruing interest on unpaid balances.

4. Can a C corp get an extension to file its return? Yes, by filing IRS Form 7004 before the original deadline, a C corp can get an automatic six-month extension to file.

5. Do all states follow the federal tax deadline? No, state deadlines can differ. Corporations should check with their state’s tax authority for specific filing requirements.

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