2023 Startup Tax Deadlines for C-Corps

The most important tax deadlines in 2023 for C-Corporation (C-Corps) are the April 18th federal Form 1120 tax return, which can be extended to October 16th, and the March, June, Sept and December Delaware Franchise estimated payments. See our detailed calendar below for other, important dates or download our ical to add the dates to your calendar.

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*Note: The federal tax deadline in 2023 falls on April 18, rather than April 15, which is a Saturday. Normally, when the tax deadline is on weekend or holiday, the deadline is moved to the next business day. However, Monday, April 17, is Emancipation Day, a holiday recognized in the District of Columbia, where the Internal Revenue Service is headquartered. The federal extension deadline for 2023 is October 16, since October 15 falls on a Sunday.


It’s important for founders to remember that even early-stage, just founded companies can have compliance and regulatory filing requirements. And it’s critical to keep your company in compliance so that you’re ready for a venture capital term sheet or M&A due diligence. You want to be make sure that your financials are in good shape and won’t delay that transaction. Plus any regulatory or compliance issues can generate penalties and paperwork – which are distractions you don’t need when you’re building a business.

To help you stay on track, here are the most important compliance deadlinesfor all small businesses, and startups in particular:

  • W2s to employees
  • 1099s to all contractors - important for all businesses!!!
  • Delaware Franchise Fee
  • State Franchise Fees
  • Federal & State Returns/Filings
  • R&D Credit and Related Studies
  • Municipal or City Filings
  • Sales Tax

That’s a lot to remember, but keeping your startup compliant with taxes and fees is cruciall to your success.


We have a more complete list above, but the most important corporate tax deadline for businesses in 2023 is the April 18th federal and state tax due date. In 2023 the date has been pushed back due to weekends and a holiday. C corporations also have estimated quarterly taxes due on April 18th, June 15th and September 15th for businesses and corporations. C-corps can file an extension with the IRS Form 7004.

Remember, even unprofitable startups need to follow these deadlines. The federal (and state) governments require filings even if your company has a loss.

What is the 2023 Form 1120 Due Date?

The due date for filing Form 1120, the corporate income tax return, for most US corporations is April 15th, 2023. However, due the 15th being a weekend, and then a holiday in DC, the deadline has been moved to April 18th, 2023. Corporations can also request an extension to file their Form 1120 until October 16th, 2023 by submitting Form 7004 to the Internal Revenue Service (IRS) by the original due date. The IRS is responsible for enforcing federal income tax laws and administering the tax system in the US.

Federal Tax Deadlines in 2023

The above calendar shows the most important Federal Tax deadlines for 2023 (it also includes some dates for Delaware C-Corps, our CPA firm’s particular client focus). The most important Federal tax deadlines to focus on for C-Corps include sending W2s to employees and 1099s to contractors, the Federal & State Returns/Filings, R&D Credits and other tax credit deadlines.

When is the last day for a startup or a Delaware C-Corp to do taxes?

The last day for a startup to file taxes is the due date for filing a Form 1120, which is the tax return form used by C-corporations (which most startups should be) to report their income, gains, losses, deductions, and credits to the (IRS), is generally the 15th day of the fourth month following the end of the corporation’s tax year. This is typically April 15th. For example, if a C-corporation has a calendar year tax year (January 1 to December 31), the due date for its Form 1120 tax return would be April 15. If a C-corporation has a fiscal year tax year (a 12-month period ending on the last day of any month except December), the due date for its Form 1120 tax return would be the 15th day of the fourth month following the end of the fiscal year.

If the due date for filing a tax return falls on a Saturday, Sunday, or legal holiday, the due date is moved to the next business day. This means that if April 15 falls on a weekend or legal holiday, the due date for filing the tax return would be the next business day.

In 2023, due to April 15th falling on a Saturday, and the next Monday being a holiday in Washington DC, the IRS has moved the last day for a startup corporation to file taxes to April 15th, 2023.

If a C-corporation is unable to file its Form 1120 tax return by the due date, it can request an extension of time to file. To obtain an extension, the corporation must file Form 7004, Application for Automatic Extension of Time To File Certain Business Income Tax, Information, and Other Returns, by the original due date of the return. The extension will generally allow the corporation to file its tax return up to six months after the original due date.

On average, one to three of our clients are acquired every month, and we what questions that the accounting firms at big, public companies are going to ask (you can access our free due diligence checklist here). Compliance is a big one! Don’t let a life-changing transaction get sidetracked by these types of issues. Of course, we recommend working with an experienced CPA like Kruze - talk to us now.

2022 Tax Compliance Deadlines For Delaware C-Corp Startups

2022 startup tax deadlines are supplied for reference purposes only, and should not be used when making decisions in 2023 or beyond. Always consult your tax professional, and see our disclaimer below. These are for Delaware C-Corporations.

How Much Does a Startup Tax Return Cost? Try Kruze Consulting’s Tax Preparation Pricing Tool.

  • JAN 31: Send 1099’ s to Contractors. Send W2’s to Employees. 1099-NEC for nonemployee compensation must also be e-filed to IRS on this date.
  • JAN 31: Send 1095-B and 1095-C forms to Employees.
  • JAN 31: Claim Research and Development Tax Credits on Prior Year Q4 Form 941, and file annual FUTA return on Form 940.
  • FEB 28: W-2 and 1099-MISC, 1099-NEC filings are due on this deadline if paper-filing (due MAR 31 if e-Filing). File Form 8809 for a 30-day extension.
  • FEB 28: IRS ACA Compliance 1094-B , 1095-B 1094-C and 1095-C filings are due on this deadline (if paper-filing, due MAR 31 if eFiling). File Form 8809 for a 30-day extension.
  • MAR 1: Delaware Annual Franchise Report filing deadline: Pay a min. of $400, +more if you have significant funding.
  • APR 15: C Corp Form 1120 Tax Return deadline. Can extend to OCT 15 with submission of form 7004.
  • APR 15: File the R&D Tax Credit Form 6765 with your tax return. Can extend to OCT 15 as mentioned above.
  • APR 15: Federal Quarterly Estimated Tax 1st installment.
  • APR 29: Claim R&D Tax Credits on Q1 Form 941.
  • JUN 1: Delaware Quarterly Estimated Franchise Tax deadline, Pay 40% of estimated annual amount (if annual amount expected to exceed $5,000).
  • JUN 15: Federal Quarterly Estimated Tax 2nd installment.
  • JUL 29: Claim R&D Tax Credits on Q2 Form 941.
  • SEP 1: Delaware Quarterly Estimated Franchise Tax deadline, Pay 20% of estimated annual amount (if annual amount expected to exceed $5,000).
  • SEP 15: Federal Quarterly Estimated Tax 3rd installment.
  • OCT 15: C Corp Form 1120 Tax Return final due date if extension was filed.
  • OCT 31: Claim your R&D Tax Credits on Q3 Form 941.
  • DEC 1: Delaware Quarterly Estimated Franchise Tax, Pay 20% of estimated annual amount (if annual amount expected to exceed $5,000).
  • DEC 15: Federal Quarterly Estimated Tax 4th installment.

How Much Does a Startup Tax Return Cost? Try Kruze Consulting Tax Preparation Pricing Tool.

Is this a tax schedule?

We’ve noticed that some startup founders are finding this page by searching for “Kruze Consulting Tax Schedules.” This is a calendar of tax deadlines for C-Corporations, and isn’t technically a “tax schedule,” as a tax schedule has a particular meaning to CPAs. However, we do think that those founders are actually looking for this list (or schedule!) of tax deadlines, so we aren’t offended.

If your Delaware C-Corp funded startup needs tax help contact us today!

View tax compliance dates for Atlanta, Austin, Boston, Chicago, Dallas, Miami, Mountain View, New York City, Palo Alto, Salt Lake City, San Francisco, San Jose, Santa Monica, Seattle, and Washington DC

How Much Does a Startup Tax Return Cost? Try Kruze Consulting's Tax Preparation Pricing Tool.

How much can your startup save in payroll taxes? Estimate your R&D tax credit using our free calculator.

Every startup is different and so are its tax compliance needs. This is only a guideline. Please consult your tax professional. IRS Circular 230 Disclaimer: To ensure compliance with IRS Circular 230, any U.S. federal tax advice provided in this communication is not intended or written to be used, and it cannot be used by the recipient or any other taxpayer for the purpose of avoiding tax penalties that may be imposed on the recipient or any other taxpayer. Copyright © Kruze Consulting

Check our 2023 Tax Deadlines For C-Corp Startups or Click for your customized tax compliance calendar by startup hub

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