Avoid penalties. Stay compliant. Build investor trust.
Keywords: Delaware startup tax deadlines, 2025 tax calendar, startup tax compliance, Form 1120, 941, 1099, franchise tax report, employee tax deadlines, sales tax startup
Launching a startup comes with a mountain of responsibilities - and staying on top of tax deadlines is one of the most important.
Whether you're a solo founder or running a growing team, missing even a single filing can lead to penalties or long-term complications.
This guide includes every major tax and compliance deadline your Delaware-registered startup needs to know - from federal and state filings to employee forms, sales tax, and what to do if you miss one.
| Date | Deadline | What It Covers |
|---|---|---|
| Jan 15 | Form 1040-ES (Q4) | Final estimated tax payment for the previous year |
| Jan 31 | Form W-2 | Send W-2s to employees |
| Jan 31 | Form 1099-NEC | Send 1099s to contractors paid $600+ |
| Mar 1 | Delaware Franchise Tax + Annual Report | Required for all Delaware C-Corps |
| Mar 15 | Form 1120 (Calendar Year) | Corporate tax return due or file Form 7004 for extension |
| Apr 15 | Form 1120 (Fiscal Year) + 1040-ES (Q1) | Q1 estimated tax + fiscal-year C-Corp taxes |
| Apr 30 | Form 941 (Q1) | Quarterly payroll tax report |
| Jun 15 | Form 1040-ES (Q2) | Q2 estimated tax payment |
| Jun 30 | Form 941 (Q2) | Quarterly payroll tax report |
| Sep 15 | Extended Form 1120 + 1040-ES (Q3) | Final corporate return if extended + Q3 estimated tax |
| Sep 30 | Form 941 (Q3) | Quarterly payroll tax report |
| Jan 15 (2026) | Form 1040-ES (Q4) | Final estimated tax for 2025 |
| Jan 31 (2026) | Form 940 (FUTA) | Annual federal unemployment tax filing |
Don’t panic - but don’t ignore it either. Here’s what to know:
Penalties & Interest - For example, late Form 1120 can cost 5% of unpaid tax per month (up to 25%). Form 941 starts at 2% for the first 5 days.
Contact the IRS - Proactively reaching out can reduce or waive penalties.
Reasonable Cause Relief - You may qualify for a penalty waiver if the reason is valid (e.g. illness, natural disaster, bookkeeping issues).
Late 1040-ES Payments - Not catastrophic, but pay ASAP to avoid stacking penalties.
If your team is remote, your tax responsibilities expand across state lines:
Register as an Employer in every state where an employee works
File State Payroll Forms - For example, California requires Form DE 9 quarterly
Use Automation Tools like Gusto, Justworks, or Rippling to handle compliance
If you sell taxable goods or services, you might owe sales tax in every state where you have a tax nexus:
Register in each state with physical or economic nexus
File returns monthly, quarterly, or annually depending on the state
Use tools like TaxJar or Avalara to automate filings and stay compliant
Answer: Yesterday.
Why it matters:
Saves time and money during tax season or due diligence
Helps you track deductible expenses properly
Builds credibility with investors who expect financial transparency
✅ Use QuickBooks, Bench, or Pilot - or hire a part-time bookkeeper early.
Staying compliant isn’t just about avoiding penalties - it’s about building operational maturity, financial hygiene, and trust with investors.
Use this 2025 guide as your roadmap for tax and compliance. Sync the dates to Google Calendar or Slack reminders. Share it with your team.
With the right systems, staying compliant is not painful - and your startup will be stronger for it.
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