What California Form 100 Is For
California Form 100 (2018) is the main corporation franchise or income tax return for entities with business activity or income linked to California. It covers C corporations, banks and financial corporations, REITs, RICs, REMICs, publicly traded partnerships, certain LLCs and LPs taxed as corporations, and some exempt organizations with taxable income. Corporations that are “doing business” in California pay the corporation franchise tax on net income at 8.84% for most corporations or 10.84% for banks and financial corporations, with a minimum franchise tax of $800, while corporations that only have California-source income but are not doing business in the state pay California corporation income tax on that California-source income without the $800 minimum.
When You’d Use California Form 100
You use California Form 100 (2018) when your corporation meets California’s filing requirements because it is doing business in the state or has California-source income. For 2018, “doing business” includes crossing any of these thresholds: California sales over $583,867 or 25% of total sales, California property over $58,387 or 25% of total property, or California payroll over $58,387 or 25% of total payroll, including your share of partnership and S corporation amounts. The return is due on the 15th day of the fourth month after your taxable year ends, usually April 15 for calendar-year corporations, and California grants an automatic six-month extension to file but not to pay, so your full tax liability is still due by the original date even if you plan to file a tax return later or resolve a past due return.
Key Rules or Details for 2018
For 2018, California generally conforms to the Internal Revenue Code as of January 1, 2015 and does not adopt most Tax Cuts and Jobs Act changes, so you must adjust from federal income to California income for items such as bonus depreciation, expanded section 179 expensing, the section 163(j) interest limitation, GILTI under section 951A, and section 965 transition tax. If your federal corporate or individual income tax return includes GILTI or section 965 income, you normally remove those amounts on the California return and may add back related deductions, documenting the adjustments so you can support your income tax position. If you use tax software, California requires you to e-file Form 100, and once a single estimated tax or extension payment exceeds $20,000 or your total California tax liability exceeds $80,000, all future payments must be made electronically, with potential 10% penalties and record-keeping penalties if you ignore e-pay rules or fail to maintain documentation, including required international forms such as federal Forms 5471, 5472, and 8975/Schedule A.
Step-by-Step (High Level)
Step 1: Confirm entity type and IDs
Decide whether you should file California Form 100 (2018), water’s-edge Form 100W, or S corporation Form 100S, based on how the entity is taxed. Confirm your California corporation number, FEIN, and Secretary of State file number so they match state records.
Step 2: Start from your federal return
Complete your federal Form 1120 and related schedules first and bring federal net income to Form 100 as the starting point. Gather supporting schedules for capital gains, asset sales, cost of goods sold, officer compensation, and any international reporting forms you must attach.
Step 3: Make California adjustments and apportionment
Use Schedule F and adjustment lines to reconcile federal net income to California net income, backing out nonconforming items like GILTI and section 965 income and applying California-specific deductions such as the dividends received deduction. If you operate in more than one state, complete Schedule R to apportion business income to California using the single-sales factor while allocating nonbusiness income under separate rules.
Step 4: Apply NOLs and credits, compute tax, and file
Apply any allowable net operating loss carryforwards and business tax credits, then compute tax at 8.84% (or 10.84% for banks and financial corporations), making sure you pay at least the $800 minimum franchise tax if you are doing business in California. Compare total tax to payments to see whether you owe more or are due a refund, answer all Schedule Q questions, attach required schedules and federal forms, have an authorized officer sign, and e-file or mail the completed package by the due date or extended due date.
Common Mistakes and How to Avoid Them
- Ignoring differences between California law and post-2015 federal changes when computing state income
- Misapplying the doing-business thresholds and wrongly avoiding or applying the $800 minimum franchise tax
- Failing to attach federal Forms 5471, 5472, or 8975/Schedule A to the California return
- Overlooking mandatory e-file and e-pay rules once thresholds are met
- Leaving Schedule Q questions blank or inconsistent with ownership or property records
What Happens After You File
After you file California Form 100 (2018), the FTB posts the return to your business account and checks it for math errors, missing schedules, and basic consistency, then applies payments against your tax liability. If you request a refund and choose direct deposit, you generally receive it faster than a paper check, provided your routing and account numbers are accurate.
If the FTB spots discrepancies, omitted attachments, or incomplete answers, it sends a notice with a response deadline, and ignoring notices can turn a simple inquiry into a full audit that looks at apportionment, combined reporting, and federal-to-California adjustments. In serious cases—especially when you fail to file or pay—the FTB can suspend or forfeit your corporation’s powers and rights in California until all tax, penalty, and interest balances are satisfied.
FAQs
How do I know if my corporation is doing business in California?
You are doing business in California for 2018 if you actively engage in transactions for profit in the state or exceed any of the sales, property, or payroll thresholds, including your share of partnership and S corporation amounts. Meeting those thresholds usually means you owe the $800 minimum franchise tax in addition to tax on net income, instead of filing only for California-source income.
Do I file California Form 100 (2018) if I had a loss or no activity?
If you are doing business in California or registered with the Secretary of State, you generally file California Form 100 (2018) even in a loss year or an inactive year. You still owe the minimum franchise tax unless you qualify for the first-year exemption for new corporations, while corporations with only California-source income but no California “doing business” file purely as an income tax return.
How do GILTI and section 965 affect my 2018 California return?
California does not conform to GILTI under IRC section 951A or the section 965 transition tax for 2018. If those items appear on your federal return, you adjust them out on Form 100 and may add back related deductions, using a short schedule that documents your calculations so you can explain them if the FTB reviews the return.
When must my corporation pay California taxes electronically?
You must pay electronically once you make a single estimated tax or extension payment of more than $20,000, or your total California tax liability exceeds $80,000. From then on, electronic payment applies to all future amounts, and paying by check can trigger a 10% penalty on the payment that should have been made electronically.
