The federal filing deadlines for a calendar-year business are generally:

For the current filing season (2025 returns filed in 2026), those dates fall as follows:

• Partnerships and S Corporations: March 16, 2026 (because March 15 is a Sunday)
• Individuals, sole proprietors, and most C Corporations: April 15, 2026

In California, your sales tax return is usually due one month after the end of the reporting period.

• Jan–Mar → Due April 30
• Apr–Jun → Due July 31
• Jul–Sep → Due October 31
• Oct–Dec → Due January 31

Each month's return is due on the last day of the following month.

• January sales → Due February 28/29
• February sales → Due March 31
• March sales → Due April 30
• And so on.

The entire year's return is due January 31 of the following year.

For most small California businesses, the key dates to remember are:

Here are some of the most common ways business owners reduce taxes before year-end:

• Equipment
• Computers
• Software
• Office supplies
• Marketing services

• Solo 401(k)
• SEP IRA
• SIMPLE IRA

• Vehicle mileage
• Home office (if eligible)
• Travel
• Professional fees
• Insurance

• Delay income when possible — if you're a cash-basis business, consider collecting some payments in January instead of December.
• Pay employee bonuses before year-end — may increase your current-year deduction.
• Maximize HSA contributions — if you're eligible for a Health Savings Account.
• Review investments — capital losses may offset capital gains.

You may have the wrong entity structure if your business is making good money and you're paying more tax than you think you should.

• What is my business profit each year?
• Am I the only owner?
• Do I have employees?
• Am I currently a sole proprietor, LLC, S Corp, or C Corp?

• Low to moderate profit: A sole proprietorship or LLC is often sufficient.
• Higher profit: An S Corp may save money on self-employment taxes.
• Outside investors or plans to retain significant earnings: A C Corp may be worth considering.

• Your profit has increased significantly.
• Your business has changed (employees, partners, new locations, etc.).
• You haven't reviewed your structure in several years.

For most businesses and individuals in the U.S., federal estimated tax payments are due on:

If a due date falls on a weekend or federal holiday, it moves to the next business day.

• Sole proprietors
• Single-member LLC owners
• Partners in partnerships
• S Corp owners who don't have enough tax withheld from wages
• Anyone expecting to owe a significant amount of tax when filing

California generally uses the same schedule, but requires uneven payment percentages (30%, 40%, 0%, 30%) unless you use an approved annualized income method.