Small Business Tax Deadlines for Ontario, California Business Owners

Written By Jose Meza

Quick Answer: For business owners in Ontario, CA, state filing deadlines generally mirror federal dates. However, the most critical oversight for local businesses is the California Annual Franchise Tax. Regardless of profit or loss, most LLCs and S-Corps must pay the minimum $800 tax to the Franchise Tax Board to remain in good standing.

Key 2026 Dates for Ontario Businesses:

  • January 31: Deadline to distribute W-2s to employees and 1099s to contractors.

  • March 16: Federal & State Returns due for S-Corps (1120-S) and Partnerships (1065). (Note: Since March 15 falls on a Sunday, the deadline moves to Monday).

  • April 15: Federal & State Returns due for C-Corps and Individuals.

  • April 15: Deadline for the $800 California LLC Tax (Form 3522) for the 2026 tax year.

The $800 California Rule Explained Many new business owners in the Inland Empire are surprised by this rule. Even if your company made $0 in revenue, the State of California generally requires an $800 minimum franchise tax payment due by April 15th. Failing to pay this on time can result in penalties and interest from the FTB.

Unsure if you owe the $800 tax? Contact Meza CPAs in Ontario today to clarify your tax obligations.

Jose Meza