Founder Tax Calendar — 2026 version
Key federal tax deadlines and timing cutoffs for calendar-year founders.
This is a practical tax calendar covering the federal filing dates, estimated payments, and timing windows that tend to matter most for startup founders across personal taxes, business returns, payroll, and R&D credits.
Download the 2026 Founder Tax Calendar
The Founder Tax Calendar is available as:
- A read-only Google Calendar
- An ICS file for Apple Calendar, Outlook, and other calendar apps
- A downloadable, printable PDF
These are the same dates and cutoffs we use internally with founder clients, shared publicly as a reference tool.
Click below to embed in your workflow
(Google Calendar, Apple Calendar, Outlook)↓
What’s included in the Founder Tax Calendar
The Founder Tax Calendar highlights the federal tax deadlines and timing cutoffs that tend to have the biggest real-world impact for founders.
It includes key personal and business tax deadlines, entity-specific filing dates for C-corporations, S-corporations, and partnerships, estimated tax payment dates, payroll and information return deadlines, and R&D-related timing cutoffs that affect when credits can actually be used.
The calendar assumes a calendar-year tax basis and focuses on federal deadlines. State- and entity-specific nuances may apply depending on your situation.
Additional resources for founders — including R&D materials, equity timing, and accounting advice — are available in the For Founders section of the site.
Founder Tax Calendar — 2026
January 2026
- January 15, 2026 — Q4 estimated tax payment (individuals)
Final installment of prior-year federal estimated income tax for individuals with non-withheld income.
February 2026
February 2, 2026 — 1099-NEC / 1099-MISC filing deadline
IRS deadline to file Forms 1099-NEC and 1099-MISC and provide copies to recipients.February 2, 2026 — W-2 forms must be furnished to employees
IRS deadline to provide Form W-2 to employees.
March 2026
March 1, 2026 — Delaware franchise tax & annual report deadline (C-Corporations)
Delaware deadline to file the annual report and pay franchise tax for C-Corporations.March 16, 2026 — Partnership tax return deadline
Federal filing deadline for Form 1065 and delivery of Schedule K-1s to partners.March 16, 2026 — S-Corporation tax return deadline
Federal filing deadline for Form 1120-S and delivery of Schedule K-1s to shareholders.March 31, 2026 — Income tax filing cutoff to enable payroll R&D credit in Q2
Income tax return must be filed by this date to allow payroll R&D credits to be claimed beginning in Q2.
April 2026
April 15, 2026 — Individual tax return deadline
Federal filing and payment deadline for individual income tax returns (Form 1040).April 15, 2026 — C-Corporation tax return deadline
Federal filing and payment deadline for C-Corporation income tax returns (Form 1120).April 15, 2026 — Q1 estimated tax payment (individuals)
First federal estimated income tax payment for the current tax year (individuals).April 15, 2026 — Q1 estimated tax payment (C-Corporations)
First federal estimated income tax payment for calendar-year C-Corporations.
June 2026
June 1, 2026 — Delaware franchise tax payment deadline (LLCs)
Delaware deadline to pay annual franchise tax for limited liability companies.June 15, 2026 — Q2 estimated tax payment (individuals)
Second federal estimated income tax payment for the current tax year (individuals).June 15, 2026 — Q2 estimated tax payment (C-Corporations)
Second federal estimated income tax payment for calendar-year C-Corporations.June 30, 2026 — Income tax filing cutoff to enable payroll R&D credit in Q3
Income tax return must be filed by this date to allow payroll R&D credits to be claimed beginning in Q3.
September 2026
September 15, 2026 — Extended partnership tax return deadline
Extended federal filing deadline for partnership returns with a valid extension.September 15, 2026 — Extended S-Corporation tax return deadline
Extended federal filing deadline for S-Corporation returns with a valid extension.September 15, 2026 — Q3 estimated tax payment (individuals)
Third federal estimated income tax payment for the current tax year (individuals).September 15, 2026 — Q3 estimated tax payment (C-Corporations)
Third federal estimated income tax payment for calendar-year C-Corporations.September 30, 2026 — Income tax filing cutoff to enable payroll R&D credit in Q4
Income tax return must be filed by this date to allow payroll R&D credits to be claimed beginning in Q4.
October 2026
October 15, 2026 — Extended individual tax return deadline
Extended federal filing deadline for individual income tax returns with a valid extension.October 15, 2026 — Extended C-Corporation tax return deadline
Extended federal filing deadline for C-Corporation income tax returns with a valid extension.
December 2026
December 15, 2026 — Q4 estimated tax payment (C-Corporations)
Fourth federal estimated income tax payment for calendar-year C-Corporations.December 31, 2026 — R&D eligibility year closes
End of the calendar tax year for determining qualified research activity eligibility.
Looking for more resources for founders?
Startup taxes, including the interplay between business and personal tax, can be complex. Whether it’s multi-state issues, international presence, tax credit claiming, or equity compensation, The Millennial CPA is seeking to make sure you make informed tax decisions that benefit you during tax season and beyond.