Startup Tax Deadlines: A Calendar for Founders
A comprehensive calendar of federal, state, and Delaware tax deadlines every startup founder needs to know. Never miss a deadline and avoid costly penalties.
Tax deadlines for startups extend far beyond the April 15th date most people know. Between federal filings, state requirements, Delaware franchise tax, payroll deposits, and equity-related deadlines, there's something due almost every month.
Missing deadlines isn't just inconvenient—it can result in significant penalties, interest charges, and even personal liability for founders. This guide provides a comprehensive calendar of the deadlines that matter most for startup founders.
Most Commonly Missed Deadline
The Delaware Franchise Tax (due March 1st) is the deadline startups miss most often. It's easy to overlook because it comes before the April 15th federal deadline, and the penalties ($200 + 1.5% monthly interest) add up quickly.
Annual Tax Deadlines
Here are the major annual tax deadlines for C-Corporations (the standard structure for VC-backed startups):
W-2s and 1099s Due
File W-2s with SSA and provide to employees. File 1099-NEC forms for contractors paid $600+ (both to IRS and recipients).
Penalties: $50-$290 per form depending on how late
Delaware Franchise Tax
Annual franchise tax and annual report due to Delaware Division of Corporations. This is NOT the same as your federal or state income tax return.
Penalty: $200 + 1.5% monthly interest. Company can lose good standing.
S-Corp and Partnership Returns (Form 1120-S, Form 1065)
If you're structured as an S-Corp or partnership, returns are due March 15th (one month before C-Corp returns). Can file for 6-month extension.
Note: Most VC-backed startups are C-Corps, so April 15th applies
C-Corp Federal Tax Return (Form 1120)
Federal corporate income tax return due. Can file Form 7004 for automatic 6-month extension (extends to October 15th).
Important: Extension is for filing only—any tax due must still be paid by April 15th
Q1 Estimated Tax Payment
First quarterly estimated tax payment due (if applicable). Required if you expect to owe $500+ in taxes for the year.
Extended C-Corp Return Due
If you filed for an extension, your federal corporate tax return is due. No further extensions available.
Weekend/Holiday Adjustments
When a deadline falls on a weekend or federal holiday, it moves to the next business day. For example, if April 15th is a Saturday, the deadline becomes Monday, April 17th.
Quarterly Deadlines
These deadlines repeat every quarter:
Estimated Tax Payments (Form 1120-W)
| Quarter | Period | Due Date |
|---|---|---|
| Q1 | January 1 - March 31 | April 15 |
| Q2 | April 1 - May 31 | June 15 |
| Q3 | June 1 - August 31 | September 15 |
| Q4 | September 1 - December 31 | December 15 |
Payroll Tax Returns (Form 941)
| Quarter | Period | Form 941 Due |
|---|---|---|
| Q1 | January 1 - March 31 | April 30 |
| Q2 | April 1 - June 30 | July 31 |
| Q3 | July 1 - September 30 | October 31 |
| Q4 | October 1 - December 31 | January 31 |
If using a payroll provider like Gusto or Rippling, they typically handle Form 941 filings automatically. However, you should verify filings are being made and maintain your own records.
Monthly Deadlines
Some tax obligations have monthly deadlines:
Payroll Tax Deposits
Federal payroll taxes (income tax withholding, Social Security, Medicare) must be deposited either monthly or semi-weekly based on your liability:
- - Monthly: If liability is under $50K, deposit by 15th of next month
- - Semi-weekly: If liability exceeds $50K, deposit within days of payroll
Payroll providers typically handle this automatically
Sales Tax Returns
If you collect sales tax, filing frequency depends on your volume in each state:
- - Monthly: Higher-volume states (typically 20th of following month)
- - Quarterly: Lower-volume states
- - Annually: Very low-volume states
Each state sets its own thresholds and due dates
Delaware-Specific Deadlines
As a Delaware corporation, you have specific obligations to the state of Delaware:
Delaware Franchise Tax & Annual Report
Due: March 1st (not April 15th!)
- File annual report online at Delaware Division of Corporations website
- Pay franchise tax using the Assumed Par Value Capital method (usually lowest)
- Minimum tax is $400; can be much higher using wrong calculation method
- Late penalty: $200 + 1.5% monthly interest on unpaid tax
For details on calculating your franchise tax, see our Delaware C-Corp guide.
Losing Good Standing
If you don't pay Delaware franchise tax, your company can lose its "good standing" status. This can prevent you from closing fundraising rounds, signing certain contracts, or completing M&A transactions. Investors will check your standing during due diligence.
State Tax Deadlines
Beyond Delaware, you may have tax obligations in other states where you have nexus (employees, offices, or significant sales). Here are common state deadlines:
State Corporate Income Tax
Most states follow the federal April 15th deadline (or extended October 15th), but some differ:
| State | Original Due Date | Extended Due Date |
|---|---|---|
| California | April 15 | October 15 (automatic 6-month) |
| New York | April 15 | October 15 (6-month) |
| Texas | May 15 (Franchise Tax Report) | November 15 |
| Massachusetts | April 15 | October 15 |
State Annual Reports
Many states require annual reports for corporations doing business there. Due dates vary widely:
- California: Statement of Information due within 90 days of original filing, then every other year by anniversary
- New York: Biennial statement due within calendar month of anniversary
- Texas: No annual report required (franchise tax report serves this purpose)
Track Your States
Keep a list of every state where you're registered to do business and their specific deadlines. Each time you hire an employee in a new state, add that state to your tracking list.
If you grant equity to employees or receive equity as a founder, there are critical tax deadlines to know:
83(b) Election Deadline
If you receive restricted stock (stock subject to vesting), you have exactly 30 days from the grant date to file an 83(b) election with the IRS. This is one of the most important tax elections for founders.
CRITICAL: This deadline cannot be extended. Missing it can cost hundreds of thousands in taxes.
409A Valuation Validity
Your 409A valuation is valid for 12 months from the valuation date, unless there's a material event (like a funding round). Plan to get updated valuations before expiration.
See our guide on 409A Valuations
Form 3921 (ISO Exercises)
If any employees exercised Incentive Stock Options during the year, you must provide Form 3921 to each employee and file with the IRS by January 31st.
Form 3922 (ESPP Transfers)
If you have an Employee Stock Purchase Plan, Form 3922 must be provided to participants and filed with the IRS by January 31st for any shares transferred in the prior year.
Extensions and Late Filing
If you can't meet a deadline, here's what you need to know about extensions:
Federal Extension (Form 7004)
What It Does
- - Extends filing deadline by 6 months
- - Automatic if filed correctly
- - No reason required
What It Doesn't Do
- - Does NOT extend payment deadline
- - Any tax owed is still due April 15th
- - Interest accrues from original due date
Penalties for Late Filing/Payment
| Penalty Type | Rate | Maximum |
|---|---|---|
| Failure to File | 5% per month of unpaid tax | 25% of unpaid tax |
| Failure to Pay | 0.5% per month of unpaid tax | 25% of unpaid tax |
| Interest | Federal short-term rate + 3% | No maximum |
File Even If You Can't Pay
If you can't pay your taxes, file the return anyway. The failure-to-file penalty (5%/month) is 10x higher than the failure-to-pay penalty (0.5%/month). Filing on time without payment is far better than not filing at all.
Staying Organized
Here's how to make sure you never miss a deadline:
Calendar Reminders
Set calendar reminders 2-4 weeks before each deadline. For critical deadlines (Delaware Franchise Tax, 83(b) elections), set multiple reminders.
Master Tax Calendar
Maintain a spreadsheet listing every tax obligation, deadline, and responsible party. Review it monthly and update as you expand to new states.
Use Payroll Providers
Services like Gusto, Rippling, and Deel handle most payroll tax filings automatically. This eliminates the risk of missing 941 deadlines and deposit requirements.
Work With a CPA
A good startup-focused CPA will track deadlines, send reminders, and ensure filings are completed on time. This is particularly valuable as you grow and have obligations in multiple states.
Fractional CFO Support
A fractional CFO can own your tax calendar, coordinate with your CPA, and ensure nothing falls through the cracks as your tax obligations become more complex.
Quick Reference: Key Dates to Remember
Federal
- - Jan 31: W-2s, 1099s
- - Apr 15: Corporate return, Q1 estimated
- - Jun 15: Q2 estimated
- - Sep 15: Q3 estimated
- - Oct 15: Extended return
- - Dec 15: Q4 estimated
Delaware & Other
- - Mar 1: Delaware Franchise Tax
- - 30 days: 83(b) elections (from grant)
- - 12 months: 409A refresh
- - Quarterly: Form 941 (payroll)
- - Varies: State returns (check each)
Related Articles
Startup Tax Guide
Complete guide to startup taxes
Delaware C-Corp
Franchise tax calculation details
409A Valuations
Stock option valuation timing
R&D Tax Credits
Payroll tax offset timing
Need Help Managing Tax Deadlines?
Eagle Rock CFO can help you track tax obligations, coordinate with your CPA, and ensure you never miss a deadline.
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