Let's be honest: tax deadlines are nobody's idea of a good time. Unfortunately, they're also non-negotiable and when you're running a startup. The last thing you need is a surprise penalty because you forgot to file your 1099s or missed a quarterly payment.
The good news is we made you a cheat sheet to make this whole ordeal a little less painful.
The airCFO 2026 Startup Tax Compliance Calendar is your guide to every important tax deadline coming your way. W-2s, estimated taxes, franchise filings, the works.
Note: Whenever a standard tax deadline falls on a Saturday, Sunday, or legal holiday, the due date is extended to the next business day.
January 2026
- JAN 31: Form W-2s are due to employees. Form 1099-NECs for nonemployee compensation are due to contractors and the IRS. File Form 8809 for a 30-day extension. (Note: Since Jan 31 is a Saturday, the deadline is technically FEB 2, but we recommend filing by Friday).
February 2026
- FEB 16: 1099-MISCs with data in boxes 8 or 10 are due to recipients. (Adjusted from Feb 15).
- MAR 2: Form 1099-MISCs are due to the IRS if you file on paper (adjusted from Feb 28) or due MAR 31, if you file electronically.
- MAR 2: San Francisco Annual Business Tax Return & Payment & Renewal are due. (Adjusted from Feb 28). If your business is registered to do business in San Francisco, SF Gross Receipts Tax is the most common filing.
- MAR 2: San Francisco Business Registration Renewal is due. (Adjusted from Feb 28).
March 2026
- MAR 2: Delaware Annual Franchise Report is due for C corporations. (Adjusted from Mar 1).
- MAR 16: New York State Mandatory First Installment of Estimated Tax is due. (Adjusted from Mar 15).
- MAR 16: New York City Business Corporation estimated tax payment (Q1) is due. (Adjusted from Mar 15).
April 2026
- APR 15: U.S. Corporation Form 1120 Tax Return is due. File Form 7004 to extend to OCT 15.
- APR 15: R&D Tax Credit Form 6765 is due (filed with your income tax return).
- APR 15: Corporation Federal Quarterly Estimated Tax (Q1) 1st installment is due.
- APR 15: California Corporation Franchise or Income Tax (Form 100) extension payment and $800 minimum tax are due.
- APR 15: California Form 100-ES Q1 Estimated Tax is due (30% of annual estimate).
- APR 15: NY State (Form CT-3) and NY City (Form NYC-2) returns are due.
- APR 30: San Francisco Business Estimated Tax Q1 installment is due.
May 2026
- JUN 1: San Francisco Business Registration Renewal is due. (Adjusted from May 31).
June 2026
- JUN 1: Delaware Quarterly Estimated Franchise Tax (40% installment) is due.
- JUN 1: Delaware LLC/LP/GP Annual Tax ($300) is due.
- JUN 15: Corporation Federal Quarterly Estimated Tax (Q2) 2nd installment is due.
- JUN 15: California Form 100-ES Q2 Estimated Tax (40% installment) is due.
- JUN 15: NY State/City estimated tax payments are due for Q2.
July 2026
- JUL 31: San Francisco Business Estimated Tax Q2 installment is due.
September 2026
- SEP 1: Delaware Quarterly Estimated Franchise Tax (20% installment) is due.
- SEP 15: Federal Quarterly Estimated Tax (Q3) 3rd installment is due.
- SEP 15: NY State/City estimated tax payments are due for Q3.
October 2026
- OCT 15: U.S. Corporation Form 1120 Tax Return final deadline (with valid extension).
- NOV 2: San Francisco Business Estimated Tax Q3 installment is due. (Adjusted from Oct 31).
December 2026
- DEC 1: Delaware Quarterly Estimated Franchise Tax (20% installment) is due.
- DEC 1: Early submission of Form 8802 for U.S. Tax Residency Certification.
- DEC 15: Federal Quarterly Estimated Tax (Q4) 4th installment is due.
- DEC 15: California Form 100-ES Q4 Estimated Tax (30% installment) is due.
- DEC 15: NY State/City estimated tax payments are due for Q4.
ROLLING: California Statement of Information; Check your entity’s specific due date here.
Have Any Questions About the Tax Compliance Calendar 2026?
Email taxteam@aircfo.com—we're here to keep your startup compliant.
Struggling to Get Tax-Compliant in 2026?
We can help. Schedule a call with our team today.
