Tax Deadlines for Startups in California

7 MIN READEditorial Policy

Taxes are definitely not at the top of any startup’s priority list, but you have to remember that company taxes are a high-risk, low-reward endeavor. You don’t get any kind of big reward for doing it right (and it’s probably not the part of your job you’re most excited about), but if you do it incorrectly, it can cause some big issues. It may be hard to do it right, especially if you don’t even know what you’re supposed to be responsible for.

Not only will you need to ensure all of your paperwork is meticulously kept but, more importantly, you’ll also have to meet several key deadlines for filings and payments.

Here’s a comprehensive timeline (based on information from the California Tax Service Center) that we’ve compiled to help you get your California-based startup tax-ready throughout the whole year, both for federal and state taxes. Human Interest is a startup as well, so we’ve lived through this ourselves! We hope you find it helpful for each month or quarter to come.

Before getting started, you’ll need to confirm if your company is registered in California, or another state. Consult with a CPA to learn about other states’ rules on taxes and deadlines if your company is registered elsewhere.

(Please note: The deadline to file and pay without penalty is extended to the next business day if regular due dates fall on a weekend or holiday.)

March 1st: Delaware Franchise Tax

This is a mandatory payment of $300 for most startups incorporated in Delaware: Link to pay online

Tip: Delaware is the leading choice for many early-stage or venture-backed startups in the United States to incorporate their businesses. Startups will generally receive the Delaware Franchise Tax bill after incorporating, and they might receive a larger tax bill than expected. This depends on the method — annual shares method or assumed par value capital method — used to calculate the franchise tax. (Note: Delaware defaults to the annual shares method if you don’t specify one or the other.)

March 15th: S Corporation Partnership & Income Tax returns due for calendar year filers

Payment must be made on time unless you file for a six-month extension prior to March 15.

California: 100S Booklet (instructions included) 565 Booklet (instructions included) 568 Booklet (instructions included)

Federal: 1120 | Instructions 1120-S | Instructions

Tip: Whether or not your company is profitable, you’re required to file a return (even if you’re operating at a loss and won’t owe taxes).  If you miss this deadline and you do not have profits then you can just file the return late. If you do have profits and, therefore, will owe taxes, you need to file an extension. If you have foreign subsidiaries, the application for extension is more complicated and it’s critical to get it right. Contact a CPA for guidance.

April 15th: California annual minimum tax ($800)

This is assuming your company is doing business in California.

Tip: This payment is for the minimum tax for 2017 and applies to all companies who registered in California in 2016 or before, regardless of a profit or loss. There is no extension available for this payment as it is independent of any tax return. Contact a CPA for guidance on when and how to pay this, or you can pay it online.

If you own a startup, you’ll need to register as a foreign entity if you’re incorporated in Delaware as soon as you start doing business in California. You can do this online, but you’ll pay additional costs for these filings and you’ll want to use expedited service to avoid a lengthy processing time.

April 18th: Corporation Income Tax returns due and tax due (for calendar year filers)

California: 100 Booklet (Instructions included)

Federal: 1120 | Instructions

April 18th: Q1 estimated tax payments due for corporations

California: 100-ES | Instructions

June 15th: Q2 estimated tax payments due for corporations

California: 100-ES | Instructions 3536 Estimated Fee for LLCs (instructions included)

September 15th: Q3 estimated tax payments due for corporations


100-ES | Instructions

September 15th: Extended due date for S Corporation Income Tax returns for calendar year filers

California: 100 Booklet (instructions included) 100S Booklet (instructions included)

September 15th: Extended due date for Partnership and LLC Income Tax returns for calendar year filers

California: 565 Partnership Booklet (instructions included) 568 Limited Liability Company Tax Booklet (instructions included)

October 15th: Extended due date for Corporation Income Tax returns (for calendar year filers)

California: 100 Booklet (instructions included)

Federal: 1120 | Instructions 1120-S | Instructions

December 15: Fourth quarter estimated tax payments due for corporations

California: 100-ES | Instructions

Deadline may vary based on registration: California Statement of Information filings

Tip: California law requires all business entities to update records via a statement filing with the California Secretary of State either every year or every two years (based on year of registration). Get more information or e-file online.

Also, remember to check with your municipality or local city government to see if there are additional fees or taxes on small businesses in general!

Get started with an affordable, full-service 401(k) plan for your startup.

Deborah Kearns is a freelance writer and editor based in Denver. Her work has appeared in USA Today, New York Times, MarketWatch, TIME, Los Angeles Times,, RISMedia,, and dozens of other print and digital publications.

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