100X: Amended Corporation Franchise or Income Tax Return (Revision)
California · FTB · Used for tax years 2024, 2025, 2026
California Form 100X is an amended corporation franchise or income tax return. It reports changes to income, deductions, taxes, payments, and credits, calculates the resulting amount due or refund, and provides an explanation of the changes.
Who files this form
Form 100X is for corporations amending a California Corporation Franchise or Income Tax Return. The form includes questions identifying whether the corporation is amending Form 100, Form 100W, or Form 100S.
The officer signing Form 100X declares that the corporation has already filed an original return.
What you'll need
- Attach all supporting forms and schedules for the items you change.
- Include federal schedules if a change was made to the federal return.
- Include the corporation name and California corporation number on every attachment.
- Refer to the forms and instructions for the taxable year being amended.
You will also need the originally reported or adjusted amounts, the net changes, and the correct amounts to complete the form's comparison columns.
Common mistakes
- Leaving the shareholder count blank when amending Form 100S. If you answer yes to question F, enter the maximum number of shareholders at any time during the taxable year.
- Not explaining each change. In Part V, enter the line number from Side 1 for each item being changed and give the reason for the change.
- Missing supporting attachments. Attach all supporting forms and schedules for changed items, including federal schedules if the federal return changed.
- Leaving identification off attachments. Include the corporation name and California corporation number on each attachment.
- Using the wrong year's reference materials. Refer to the forms and instructions for the taxable year being amended.
Questions people ask
How do I show the amounts I am changing?
Parts I and II have columns for the originally reported or adjusted amount, the net change, and the correct amount. Explain the changes in Part V.
What if the corporation's information is unchanged from the original return?
In Part V, item 1, write “Same” if the original return's name, address, and identifying numbers are the same as those shown on the amended return.
What federal return information does Form 100X ask for?
The form asks whether the corporation filed an amended IRS return for the same reason, whether the IRS has advised that the original federal return is, was, or will be audited, and whether the amendment is based on a final federal determination. If it is based on a final federal determination, enter the determination date or dates.
How does the form calculate an amount due or a refund?
If line 21 is greater than line 30, subtract line 30 from line 21 and enter the amount due on line 31. If line 30 is greater than line 21, subtract line 21 from line 30 and enter the refund on line 32.
Who signs the amended return?
The form has a signature area for a corporation officer, including the officer's title, date, and telephone number. It also has a separate area for a paid preparer's information and signature.