Taxes can be one of the most daunting aspects of running a startup. Deadlines pile up, requirements vary by state and entity type, and it’s all too easy to let important filings slip through the cracks. At airCFO, we understand how overwhelming it can be to keep track of it all—especially while juggling the many demands of growing your business.

That’s why we’ve created the airCFO 2025 Startup Tax Compliance Calendar. This guide breaks down the key tax deadlines and filing requirements your startup needs to know for the year ahead. Whether you’re filing W-2s, navigating quarterly estimated taxes, or meeting franchise obligations, we’re here to help you stay on top of it all.

With this calendar, that you can add to your Google account, you’ll have a clear roadmap to tax compliance in 2025—saving you time, reducing stress, and letting you focus on what matters most: building your business. While this calendar provides a helpful roadmap, it’s always important to consult a tax professional for advice specific to your business’s unique circumstances. Let’s get started!

The airCFO 2025 Startup Tax Compliance Calendar

January 2025

• JAN 31: Form **W-2’**s are due to employees whether you e-file or paper file. Form 1099-NEC’s for nonemployee compensation (usually to contractors) are due whether you e-file or paper file. File Form 8809 for a 30-day extension.

February 2025

• FEB 28: Form 1099-MISC’s are due, if you file on paper (or due MAR 31, if you file electronically). File Form 8809 for a 30-day extension. 1099-MISC’s with no data in boxes 8 or 10 are due to recipients by JAN 31. Forms containing data in boxes 8 or 10 are due FEB 15.
• FEB 28: San Francisco Annual Business Tax Return & Payment are due, if your business is registered to do business in San Francisco. SF Gross Receipts Tax is the most common filing.

March 2025

• MAR 1: Delaware Annual Franchise Report is due for C corporations incorporated in Delaware.
• MAR 15: New York State Mandatory First Installment of Estimated Tax for Corporations is due, if New York C corporations have more than $1,000 tax after credits for the second. preceding tax year. New York City Business Corporation estimated tax payment is due for Q1, if the second preceding year’s tax was more than $1,000.

April 2025

• APR 15: U.S. Corporation Form 1120 Tax Return is due. File Form 7004 to extend to OCT 15, but tax payment cannot be extended.
• APR 15: File the R&D Tax Credit Form 6765 with your tax return. This form is part of income tax filing, so extending Form 1120 is also extending this form.
• APR 15: Corporation Federal Quarterly Estimated Tax 1st installment is due, if annual estimated tax is $500 or more.
• APR 15: California Corporation Franchise or Income Tax (Form 100) extension payment is due. The minimum franchise tax is $800. Extension for time to file the return (not pay tax) is also due.
• APR 15: California Form 100-ES Q1 Estimated Tax is due (30% of annual estimated tax).
• APR 15: New York State General Business Corporation Franchise Tax Return **Form CT-3** is due and New York City Business Corporation Tax Return Form NYC-2 is due. These filings (not tax payments) can be extended to OCT 15.
• APR 30: San Francisco Business Estimated Tax Q1 installment is due.

May 2025

• May 31st - San Francisco Business Registration Renewal is due.

June 2025

• JUN 1: Delaware Quarterly Estimated Franchise Tax is due if the annual tax due is expected to exceed $5,000. Pay 40% of the estimated annual amount.
• JUN 1: Limited Liability Companies, Limited Partnerships, and General Partnerships that were formed or registered in Delaware are required to pay an annual tax of $300. There is no requirement to file an Annual Report.
• JUN 15: Corporation Federal Quarterly Estimated Tax 2nd installment is due, if annual estimated tax is $500 or more.
• JUN 15: California Form 100-ES Q2 Estimated Tax is due (40% of estimated tax). California does not require a Q3 installment.
• JUN 15: New York State and New York City estimated tax payments are due for Q2.

July 2025

• JUL 31: San Francisco Business Estimated Tax Q2 installment is due.

September 2025

• SEP 1: Delaware Quarterly Estimated Franchise Tax is due if the annual tax due is expected to exceed $5,000. Pay 20% of the estimated annual amount.
• SEP 15: Corporation Federal Quarterly Estimated Tax 3rd installment is due, if annual estimated tax is $500 or more.
• SEP 15: New York State and New York City estimated tax payments are due for Q3.

October 2025

• OCT 15: U.S. Corporation Form 1120 Tax Return final due date if extension has been filed.
• OCT 31: San Francisco Business Estimated Tax Q3 installment is due. San Francisco does not require a Q4 installment.

December 2025

• DEC 1: Delaware Quarterly Estimated Franchise Tax is due if the annual tax due is expected to exceed $5,000. Pay 20% of the estimated annual amount.
• DEC 1: Early submission of Form 8802 to apply for a current year Form 6166 Certification of U.S. Tax Residency, if your foreign customers request this certification.
• DEC 15: Corporation Federal Quarterly Estimated Tax 4th installment is due, if annual estimated tax is $500 or more.
• DEC 15: California Form 100-ES Q4 Estimated Tax is due (30% of estimated tax).
• DEC 15: New York State and New York City estimated tax payments are due for Q4.

ROLLING: California Statement of Information; Look up your entity’s due date **here.**

Have Any Questions About the Tax Compliance Calendar?

If you have any questions about airCFO Tax Compliance Calendar, please email taxteam@aircfo.com, they are here to help!

Want to Get Tax-Compliant in 2025?

We can help—schedule a call with our team today.