100S: California S Corporation Franchise or Income Tax Return (2025)
California · FTB · Used for tax years 2025
Form 100S is the California S Corporation Franchise or Income Tax Return for 2025. It reports income, state adjustments, deductions, credits, taxes, and payments to determine the corporation's refund or amount due.
What you'll need
Have the corporation’s name, address, California corporation number, FEIN, and California Secretary of State file number available.
Depending on the items reported, the form calls for:
- Federal Form 1120-S, page 1, and supporting schedules if Schedule F on Form 100S is not completed.
- Schedule D (100S) for the capital gains and tax entries that require it.
- Schedule B (100S) for depreciation and amortization adjustments and the Section 179 expense deduction.
- Schedule H (100S) for the dividends received deduction or water’s-edge dividend deduction.
- Schedule C (100S) for the credits totaled on line 25.
- Schedule R if apportioning or allocating income.
- Forms 592-B and/or 593 for the 2025 withholding entry.
- Federal Form 8886 for each transaction if the return includes a reportable or listed transaction.
- Federal Form 8825 for net rental real estate income or loss on Schedule K.
Attach supporting schedules where the form requests them, including for other additions and deductions.
Common mistakes
- Leaving required business details blank. Schedule Q specifically says not to leave blank the principal business activity code or the maximum number of shareholders at any time during the year.
- Treating line 37 as a total. The form warns that line 37 is for use tax and is not a total line.
- Overlooking a BOE-100-B filing. A “Yes” answer to the real-property ownership or control questions in Side 1, item B, requires filing a BOE-100-B statement. The form warns that penalties may apply.
- Using the wrong figures for cost of goods sold. Schedule V says to use California figures and federal procedures.
Questions people ask
Can an overpayment be applied to next year’s estimated tax?
Yes. On the 2025 return, line 42 lets you enter the amount of the line 41 overpayment to credit toward 2026 estimated tax.
Does the form offer direct deposit for a refund?
Yes. The refund area includes fields for a routing number, checking or savings account type, and account number. It directs you to the instructions for direct deposit.
Must every corporation complete Schedule L and Schedule M-1?
Not necessarily. The form says the corporation may not be required to complete these schedules and refers to their instructions for reporting requirements.
What if the method for determining inventory quantities, costs, or valuations changed?
Schedule V asks whether there was a change between opening and closing inventory. If you answer “Yes,” attach an explanation.
Who signs the return?
The signature area calls for an officer’s signature, title, date, and telephone number. The officer’s email address is optional. There is also a separate paid preparer section.