California Form 100W is the California Corporation Franchise or Income Tax Return — Water’s-Edge Filers, and every C corporation that has made a valid water’s-edge election under R&TC Section 25113 must file it with the California Franchise Tax Board (FTB) instead of the standard Form 100. The form lets a unitary group exclude most foreign affiliates from its California combined report, which can sharply lower the apportioned tax base for U.S. parents with profitable overseas subsidiaries.
Filing the wrong return — or fumbling Schedule H, Schedule P, or the Form 100-WE election attachment — can void a 7-year election, trigger the $800 minimum franchise tax twice, and invite a Notice of Proposed Assessment. The FTB processes more than 90,000 corporate returns each year, and water’s-edge filers face one of the highest schedule-error rates of any California business return, according to FTB e-file data published in the 2025 Form 100W Booklet.
Here is what you will learn in this guide:
- 📌 The exact line-by-line meaning of every box on the 2025 Form 100W
- 🧾 Which schedules (H, P, R, D, J, 3885, 2416, 2424) you must attach and why
- 🌐 How to e-file, paper-file, and pay through FTB Web Pay
- 🧮 Three full filled-out scenarios — first-time electors, unitary groups, and election terminations
- ⚠️ The 10 most common mistakes that void elections, plus 12 field-level FAQs
What Form 100W Is and Who Must File It
Form 100W is the California franchise or income tax return reserved for C corporations that have elected, under R&TC Sections 25110 and 25113, to compute their California-source income on a water’s-edge basis rather than on a worldwide unitary basis. The 2025 revision was issued by the FTB in late 2025 and carries the form footer “7001253” near the bottom of page 1, which is how preparers confirm they are using the current version.
A corporation must file Form 100W (instead of Form 100) when three things are true: it is doing business in California or is incorporated in California, it is part of a unitary business with one or more affiliates, and a valid water’s-edge election under R&TC Section 25113 is in effect for the taxable year. The election is made on Form 100-WE, which is signed by an officer and stapled to the back of the very first Form 100W filed under the election.
The election lasts 84 months (7 calendar years) and renews automatically unless terminated under R&TC Section 25113(c). S corporations do not file Form 100W; they file Form 100S and attach Form 100-WE if they want water’s-edge treatment. Tax-exempt organizations file Form 109, not Form 100W.
The form solves a specific problem: it lets a U.S. parent legally exclude foreign affiliates that have no California nexus from the California combined report, so only U.S. and partially-included foreign income is apportioned. Without the election, California would otherwise require worldwide combined reporting under R&TC Section 25101, which can pull profitable foreign subsidiaries’ income into the California tax base.
Before You Start: Documents and Information You Need
Gather every supporting document before you open the form, because Form 100W cross-references at least eight federal and California schedules. Missing any single item can stall the return at the FTB scanning stage and bump processing from 4 weeks to 12 weeks or more, per the FTB e-file forms list.
Use this pre-filing checklist:
- A complete copy of federal Form 1120 (and all attached schedules), because California starts from federal taxable income on Side 4, Line 1; missing it triggers an automatic adjustment notice.
- The corporation’s California corporation number (7 digits) and federal employer identification number (FEIN), because the FTB matches both to its entity database; mismatches stall processing.
- The signed Form 100-WE for first-year filers, because without it the FTB treats the return as Form 100 and issues a worldwide-basis assessment.
- Detailed Subpart F income statements and Section 951A GILTI workpapers for every controlled foreign corporation (CFC), because partially-included CFCs flow onto Schedule R apportionment factors.
- Apportionment workpapers showing California and everywhere sales, payroll, and property (single-sales factor for most filers), because Schedule R needs those numbers to the dollar.
- Dividend records for the past 12 months from every foreign subsidiary, partnership, or REIT, because Schedule H (100W) computes the dividend deduction.
- Prior-year California tax return and any net operating loss (NOL) carryover schedule, because Side 2, Line 19 ties to the prior-year NOL balance.
- Estimated tax payment vouchers (Form 100-ES) and any 2024 overpayment credited forward, because Side 2, Line 32 needs the exact dollar total.
- Credit certificates (research, low-income housing, etc.) and Schedule P (100W) workpapers, because credits are limited by tentative minimum tax.
- Officer signature authority (board minutes or POA Form 3520-BE), because an unsigned Form 100W is treated as unfiled and accrues late penalties.
Where to Get the Form and How to Access It
The official 2025 Form 100W lives on the FTB website as a fillable PDF at the FTB 2025 Form 100W page, and the full instruction booklet (with Schedules H, P, and Form 100-WE) is at the 2025 Form 100W Booklet. Always download the PDF directly from ftb.ca.gov rather than a third-party aggregator, because aggregators often host expired revisions that the FTB scanner will reject.
Approved tax software (CCH Axcess, GoSystem, Lacerte, ProSystem fx, UltraTax, and Drake) all support e-file for Form 100W, per the FTB e-file forms list. Large filers can also use the FTB’s MeF (Modernized e-File) channel through their software vendor; the FTB does not offer a free direct-entry portal for corporate returns.
If you want to paper-file, print the PDF on plain white 8.5” × 11” paper, single-sided, with no shrink-to-fit scaling, because the OCR barcode at the bottom of each page must remain at 100% scale. Staple Form 100-WE to the back of page 6 for first-year electors, and mail to the address on Side 6 of the form: Franchise Tax Board, PO Box 942857, Sacramento, CA 94257-0500 for returns with a payment, or PO Box 942857, Sacramento, CA 94257-0500 for refund/zero-balance returns.
Step-by-Step: How to Fill Out Form 100W Line by Line
The 2025 Form 100W is six pages. Side 1 captures the entity header and basic election questions, Side 2 computes tax and payments, Side 3 is Schedule J (add-on taxes) and Schedule Q (questions), Side 4 is Schedule F (federal-to-California reconciliation), Side 5 is Schedule M-1 (book-to-tax) and Schedule L (balance sheet), and Side 6 is Schedule M-2 (retained earnings) and the signature block. Work top to bottom, page by page, and never skip a field, because the FTB scanner reads every box.
Taxable Year and Fiscal-Year Boxes (Top of Side 1)
The taxable year boxes ask for the beginning and ending dates of the corporation’s California taxable year. Enter the beginning date in the left box and the ending date in the right box, both formatted MM/DD/YYYY with leading zeros (for example, 01/01/2025 and 12/31/2025). Calendar-year filers can leave both blank and rely on the printed “2025” year header.
For example, Acme Tech Inc., a calendar-year filer, leaves both date boxes blank because the printed year already says 2025. Pacific Imports Corp., a fiscal-year filer with a July–June year, writes 07/01/2025 and 06/30/2026. The nuance is that a short-period return (created by a merger or a change in accounting period) also requires you to check the “Short period” box on Side 1, Question A.
A common mistake is leaving the boxes blank for a fiscal-year filer, which causes the FTB to default the return to a calendar year and issue a delinquency notice for the wrong period. A frequent misconception is that the printed “2025” overrides any fiscal-year date entered — it does not; the dates you enter always control.
Question A: Reason for Filing (Side 1)
Question A asks why this Form 100W is being filed: first return, final return, amended return, or short period. Check exactly one box, and if the return is a final return, also enter the dissolution date in the box provided. The FTB uses this checkbox to route the return to the correct unit (regular processing, dissolution unit, or amended-return unit).
For example, Acme Tech Inc. checks no box because this is a normal continuing return. Sunset Holdings LLC checks “Final return” and writes 11/30/2025 as the dissolution date. The nuance is that a “Final return” must be paired with FTB Form 3555 (Request for Tax Clearance) for some entities, and skipping it can leave the corporation on the FTB’s active rolls.
A common mistake is checking “Amended return” on the original return because the preparer is “amending” their own draft — this routes the return to the amended-return unit and delays processing 8–12 weeks. A misconception is that checking “First return” is required for every newly-electing water’s-edge filer, but “First return” only applies to the corporation’s first-ever California return, not its first water’s-edge year.
Question D: Water’s-Edge Election Confirmation
Question D is the most important box on the entire form for water’s-edge filers, and it states: “This return is being filed pursuant to a water’s-edge election under R&TC Section 25113.” You must check the Yes box, or the FTB will process the return as a Form 100 and assess worldwide combined tax. If this is the first year of the election, you must also attach a signed Form 100-WE to the back of the return.
For example, Acme Tech Inc., in year 3 of its 7-year election, checks Yes and does not attach a new Form 100-WE because the original is on file. Globex Manufacturing, filing for the first water’s-edge year, checks Yes and staples a freshly-signed Form 100-WE listing all 14 unitary affiliates. The nuance is that mid-year acquisitions of new affiliates require an updated 100-WE listing those new entities — not a new election.
A common mistake is leaving Question D blank because the preparer assumed the form name itself “Water’s-Edge Filers” was enough proof. The consequence is a worldwide-basis assessment that can take 18 months and a formal protest to undo. A misconception is that a single Form 100-WE binds every affiliate forever, but the election expires after 84 months unless silently renewed by continued filing under R&TC Section 25113(c).
California Corporation Number and FEIN (Header Block)
The header block on Side 1 asks for the corporation name, address, California corporation number (7 digits, no dashes), and FEIN (9 digits, formatted XX-XXXXXXX). Enter the legal name exactly as registered with the California Secretary of State, including punctuation; do not use a “doing business as” name unless the entity has formally registered the DBA.
For example, Acme Tech Inc. enters its California corporation number as 2345678 and its FEIN as 82-1234567. The nuance: LLCs taxed as corporations enter the 12-digit California Secretary of State number left-justified, leaving the rightmost boxes blank. A common mistake is entering the FEIN with a leading “EIN” or extra characters, which causes the OCR to reject the field.
A misconception is that the entity name must match the IRS records exactly — California cares about the Secretary of State name, not the IRS name, and a mismatch with the FEIN database alone will not block the return.
Side 2, Line 1 — Net Income (Loss) Before State Adjustments
Line 1 starts with federal net income from Form 1120, Line 28 (taxable income before NOL and special deductions). This number flows from Schedule F (Side 4), Line 30, so most preparers fill out Side 4 first and then transfer the result. Enter whole dollars only, with negative numbers in parentheses (for example, (125,400)).
For example, Acme Tech Inc. enters $4,250,000 on Line 1 because that’s its federal taxable income before NOL. Globex Manufacturing, with a federal loss, enters (875,000). A nuance: Subpart F income and partial CFC inclusions modify this starting number through Schedule F, so do not adjust Line 1 directly — adjust on Schedule F.
A common mistake is using Form 1120, Line 30 (federal taxable income after NOL) instead of Line 28, which double-counts the federal NOL and California NOL. A misconception is that consolidated federal returns let you skip Schedule F — they do not; California requires a separate-company starting point per R&TC Section 25101.5.
Side 2, Line 2–17 — California Adjustments and Net Income
Lines 2 through 17 walk you from federal net income to California net income subject to apportionment. Key adjustments include water’s-edge dividend deductions (Line 10, from Schedule H), the dividends-received deduction, and California-specific add-backs for items like the federal Section 199A pass-through deduction. Each line has a one-for-one match in Schedule F, so always reconcile the two before signing.
For example, Acme Tech Inc. enters $120,000 on Line 10 for its Schedule H dividend deduction from a 50%-included Singapore CFC. The nuance: bonus depreciation is decoupled in California, so Line 6 add-backs are common for filers using IRC Section 168(k). A common mistake is forgetting the Schedule H (100W) dividend deduction entirely, which inflates California net income and overpays tax.
A misconception is that California “conforms” to federal taxable income — it does not for many items, including bonus depreciation, Section 174 R&D capitalization timing, and the IRC Section 163(j) interest limit.
Side 2, Line 18 — Net Income (Loss) for State Purposes
Line 18 is California net income before apportionment, computed as Line 1 plus or minus Lines 2–17. This is the figure you carry to Schedule R, Line 1, for apportionment. Enter the number in whole dollars, with parentheses for losses.
For example, Acme Tech Inc. enters $4,130,000. Globex Manufacturing enters (750,000) because of a federal loss adjusted upward for California decoupling items. A nuance: a unitary combined group computes a single Line 18 for the whole group, then apportions to California, and each taxpayer member’s share appears on its own Schedule R-7.
A common mistake is computing Line 18 separately for each affiliate, which violates combined reporting principles in FTB Pub. 1061. A misconception is that water’s-edge means separate-company filing — it does not; it just narrows the combined group to U.S. and partially-included foreign entities.
Side 2, Line 19 — Net Operating Loss Deduction
Line 19 is the California NOL deduction, taken from the corporation’s NOL carryover schedule. California suspends NOL deductions for taxable years 2024 and 2025 for taxpayers with California net business income of $1 million or more, per the 2025 Form 100W Booklet. Enter zero if the suspension applies.
For example, Acme Tech Inc., with $4.13M California net income, enters 0 on Line 19 because the suspension blocks its $200,000 NOL carryover. Tiny Holdings LLC, with $400,000 net income, enters (40,000). The nuance: suspended NOLs gain an extra year of carryover, so they are not lost — just deferred.
A common mistake is taking the full NOL despite the suspension, which the FTB will assess back with interest. A misconception is that water’s-edge NOLs are “frozen” in place at election; they are not — they continue to carry forward under R&TC Section 24416.
Side 2, Line 22 — Tax (8.84% Franchise Tax)
Line 22 is the California franchise tax, computed as 8.84% of Line 21 (apportioned California net income). Banks and financial corporations pay 10.84% under R&TC Section 23186; all other water’s-edge filers pay 8.84%. Enter whole dollars.
For example, Acme Tech Inc., with $1,650,000 of California-apportioned income, enters $145,860. Pacific Bank Holdings enters $178,860 on the same income because of the 10.84% rate. The nuance: minimum franchise tax of $800 applies if computed tax is below $800.
A common mistake is using the federal 21% rate by accident, which overstates California tax by roughly 2.4× and creates a refund that the FTB will challenge. A misconception is that an apportionment factor of zero exempts the corporation — even a zero-factor filer pays the $800 minimum if it is doing business in California.
Side 2, Line 23 — Schedule P (100W) Tentative Minimum Tax
Line 23 captures the alternative minimum tax (AMT) computed on Schedule P (100W), per the Schedule P (100W) instructions. California’s corporate AMT applies at 6.65% of alternative minimum taxable income above the exemption. Enter the larger of regular tax or tentative minimum tax.
For example, Acme Tech Inc. enters $145,860 because regular tax exceeds AMT. Globex Manufacturing, with heavy depreciation preferences, enters $98,500 AMT because it exceeds regular tax of $72,000. A nuance: water’s-edge filers have unique Schedule P adjustments for foreign dividend deductions.
A common mistake is omitting Schedule P entirely for “small” corporations — California AMT has no small-corporation exemption like the federal version. A misconception is that the federal corporate AMT repeal in 2017 ended California AMT — California still imposes it under R&TC Section 23455.
Side 2, Line 32 — Estimated Tax Payments
Line 32 totals all 2025 estimated tax payments made via Form 100-ES, plus any 2024 overpayment credited forward. Estimated tax is due in four installments on the 15th day of the 4th, 6th, 9th, and 12th months of the taxable year.
For example, Acme Tech Inc. enters $140,000 — four $35,000 quarterly payments. Globex Manufacturing enters $0 because it is in its first year and used the prior-year safe harbor. A nuance: the first installment must be at least 30% of total tax, the second 40%, the third 0%, and the fourth 30%.
A common mistake is including the $800 minimum franchise tax payment for a first-year corporation on Line 32 — first-year corporations are exempt from the minimum, so there should be no such payment. A misconception is that estimated payments can be irregular as long as they total 100% by year-end; the FTB assesses underpayment penalties under R&TC Section 19142 for any short installment.
Schedule H (100W) — Dividend Income Deduction
Schedule H (100W) computes the partial dividend deduction allowed for water’s-edge filers under R&TC Sections 24411 and 25106. The deduction can reach 75% of qualifying foreign dividends from non-included CFCs, and 100% for dividends from members of the water’s-edge group. Complete one line per dividend payer.
For example, Acme Tech Inc. receives $200,000 from its Singapore CFC (75% deductible) and enters $150,000 as the deduction. The nuance: dividends from “tax haven” jurisdictions on the FTB’s list are not eligible for the 75% deduction. A common mistake is claiming 100% deduction on partially-included CFC dividends, which the FTB flags on examination.
A misconception is that Schedule H mirrors the federal dividends-received deduction; it does not, and the percentages differ sharply.
Schedule R — California Apportionment
Schedule R apportions the combined group’s business income to California using the single-sales factor (for most industries) under R&TC Section 25128.7. Enter California sales on Line 1a, everywhere sales on Line 1b, and compute the California percentage on Line 2. Service businesses use market-based sourcing under R&TC Section 25136.
For example, Acme Tech Inc. shows $10M California sales and $25M everywhere sales for a 40% California factor. The nuance: throwback sales rules do not apply to water’s-edge filers under R&TC Section 25135. A common mistake is using cost-of-performance sourcing for services, which California abandoned in 2013.
A misconception is that property and payroll factors still matter — they do only for narrow industries (extraction, banks) and most filers use single-sales only.
Schedule J — Add-On Taxes and LIFO Recapture
Schedule J on Side 3 captures add-on taxes such as LIFO recapture, built-in gains tax (rare for C corps), and the credit recapture for low-income housing or research credits. Enter the total on Line 1 of Schedule J and carry it to Side 2, Line 26.
For example, Sunset Holdings LLC, terminating its election, enters $45,000 of LIFO recapture. The nuance: recapture is spread over 4 years under federal rules, and California conforms.
Form 100-WE — The Water’s-Edge Election Itself
Form 100-WE is the actual election document. Enter the electing corporation name, California corporation number, FEIN, address, the election beginning date (MM/DD/YYYY), and have an officer sign and date it. Check the box if a common parent is electing on behalf of a controlled group, and list every member.
For example, Globex Manufacturing’s parent enters 01/01/2025 as the beginning date and lists 14 affiliates. The nuance: if group members have different fiscal years, the election begins on the latest member’s fiscal-year start. A common mistake is failing to list new affiliates acquired mid-year, which can void the election as to those entities.
Signature Block (Side 6)
The signature block requires an officer’s signature, printed name, title, date, and daytime phone number. The paid preparer signs separately and enters their PTIN, firm name, firm FEIN, and firm address. Unsigned returns are treated as unfiled under R&TC Section 18621.
A common mistake is having a non-officer (controller, CFO of a subsidiary) sign — only an officer of the taxpayer may sign. A misconception is that an electronic signature is invalid; the FTB accepts MeF e-signatures and Form 8453-C signature authorization.
Three Filled-Out Examples Using Real Scenarios
Scenario 1 — Acme Tech Inc., a First-Time Water’s-Edge Electors
Acme Tech Inc. is a California-headquartered software company with a Singapore CFC and a U.K. subsidiary, and 2025 is its first water’s-edge year.
| Form Section | What Acme Tech Enters |
|---|---|
| Taxable year | 01/01/2025 to 12/31/2025 |
| Question A | No box checked (continuing return) |
| Question D (Water’s-Edge) | Yes — Form 100-WE attached |
| California corp number / FEIN | 2345678 / 82-1234567 |
| Side 2, Line 1 (Federal NI) | $4,250,000 |
| Side 2, Line 10 (Sch H deduction) | $150,000 |
| Side 2, Line 18 (CA net income) | $4,130,000 |
| Schedule R Line 2 (CA factor) | 40% |
| Side 2, Line 22 (Tax @ 8.84%) | $145,860 |
| Side 2, Line 32 (Est. payments) | $140,000 |
| Form 100-WE election date | 01/01/2025 |
Scenario 2 — Globex Manufacturing, a Unitary Group with 14 Affiliates
Globex Manufacturing is the common parent of a 14-entity controlled group with U.S. plants in 9 states and partial-inclusion CFCs in Mexico and Canada.
| Form Section | What Globex Enters |
|---|---|
| Taxable year | 01/01/2025 to 12/31/2025 |
| Question A | No box checked |
| Question D | Yes — Form 100-WE filed in 2020, year 6 of election |
| Filing form | Schedule R-7 group return |
| Side 2, Line 1 | $(875,000) federal loss |
| Side 2, Line 6 (CA decoupling) | $125,000 add-back |
| Side 2, Line 18 | $(750,000) |
| Schedule R Line 2 (CA factor) | 18% |
| Side 2, Line 22 | $0 (loss year) |
| Side 2, Line 30 (Min. tax) | $800 per taxpayer member |
| Schedule H deduction | $0 (no qualifying dividends) |
Scenario 3 — Sunset Holdings LLC, Terminating the Election
Sunset Holdings LLC is a C corporation that elected water’s-edge in 2018 and is now terminating because its foreign subsidiaries have flipped to losses.
| Form Section | What Sunset Holdings Enters |
|---|---|
| Taxable year | 01/01/2025 to 11/30/2025 (short period) |
| Question A | Final return — dissolution date 11/30/2025 |
| Question D | Yes — last year of water’s-edge filing |
| Termination notice | Attached letter under R&TC §25113(c) |
| Side 2, Line 1 | $1,200,000 |
| Schedule J (LIFO recapture) | $45,000 |
| Side 2, Line 22 | $106,080 |
| Schedule R Line 2 | 25% |
| Side 2, Line 32 | $95,000 |
| Form 3555 (Tax Clearance) | Attached |
How to File the Completed Form 100W
You can file Form 100W three ways: e-file through approved software, paper-file by mail, or (rarely) hand-deliver to an FTB field office. The FTB strongly prefers e-file because of faster processing and lower error rates, and most software vendors support it via the FTB business e-file forms list.
E-file: Use CCH Axcess, GoSystem, Lacerte, ProSystem fx, UltraTax, or Drake. There is no FTB filing fee for e-file. Processing time is typically 4–6 weeks. Keep the FTB acknowledgment file as proof of filing — that’s your only proof. Pay any balance due via FTB Web Pay (free ACH from a checking account), credit card (2.3% fee), or EFT (mandatory for taxpayers owing $20,000+ in any installment).
Paper filing: Print on plain white paper, no staples in the barcode area, and mail with payment to Franchise Tax Board, PO Box 942857, Sacramento, CA 94257-0500. Returns without payment go to PO Box 942857, Sacramento, CA 94257-0500 (same PO Box; the FTB sorts internally). Use certified mail with return receipt as proof of timely filing — postmark date is the filing date under R&TC Section 18416. Processing time runs 8–12 weeks.
In-person: Walk the return into any FTB field office (Sacramento, Oakland, San Diego, Santa Ana, West Covina, San Francisco, San Jose, Fresno, Los Angeles). Bring two copies and have the front desk date-stamp one for your records. No fee to file; no payment accepted in person — pay separately via Web Pay.
The original return due date is the 15th day of the 4th month after the close of the taxable year (April 15 for calendar-year filers), and California grants an automatic 7-month extension to the 15th day of the 11th month (November 15), per FTB Web Pay guidance. The extension is automatic — no form is needed — but it extends time to file, not time to pay.
What Happens After You File
After the FTB accepts the return, you’ll receive an acknowledgment within 48 hours for e-file or a Notice of Tax Return Acceptance within 8–12 weeks for paper. The FTB then runs its scanning and matching cycle, comparing your federal Form 1120 (received via the IRS Federal/State Match) to your California Form 100W. Mismatches generate a Notice of Proposed Assessment (NPA) within 6–18 months.
If you owe a balance, the FTB sends a billing notice with interest accruing from the original due date at the FTB’s adjusted rate (currently around 8% annually). If you overpaid, the refund typically issues within 4–6 weeks of acceptance, and you can credit it forward to the next year via Side 2, Line 39.
The water’s-edge election continues automatically into the next year unless you affirmatively terminate under R&TC Section 25113(c). At month 84 of the election, the FTB does not send a renewal notice — silent continuation is the rule. If the FTB selects the return for audit, expect a letter within 18–30 months; California’s statute of limitations is 4 years from the original due date, or 6 years for substantial omissions.
Mistakes to Avoid When Filling Out Form 100W
- Filing Form 100 instead of Form 100W. The FTB processes the return on a worldwide basis and pulls in foreign affiliate income.
- Forgetting to attach Form 100-WE in year 1. The election is treated as not made, voiding 7 years of planning.
- Not checking Question D as Yes. The FTB defaults the return to worldwide and issues an NPA.
- Using federal taxable income from Line 30 instead of Line 28. Double-counts the federal NOL.
- Skipping Schedule H (100W). Overstates California net income by the missed dividend deduction.
- Taking a suspended NOL. California disallows NOL deductions in 2024–2025 for filers with $1M+ net business income.
- Using cost-of-performance sourcing. California requires market-based sourcing under R&TC §25136.
- Omitting Schedule P (100W). California AMT applies even when federal AMT does not.
- Missing the $800 minimum. Even loss years require the minimum franchise tax (except the first year).
- Late filing without extension payment. Extension is to file, not to pay; late-payment penalty is 5% plus 0.5%/month.
- Wrong officer signature. A subsidiary controller cannot sign for the parent; the FTB treats it as unfiled.
- Mailing without certified mail. Without proof of mailing, the FTB postmark date governs and may be days late.
Do’s and Don’ts
- Do download the form fresh from ftb.ca.gov every January to catch revisions, because mid-year revisions do happen.
- Do reconcile Schedule F (Side 4) before completing Side 2, because Side 2 depends entirely on Schedule F totals.
- Do keep a signed PDF copy of Form 100-WE with corporate minutes, because the original may need to be re-presented in audit years later.
- Do pay via Web Pay at least 2 business days before the due date, because ACH posting takes 1–2 days.
- Do e-file when possible, because paper returns have a 12% scanning-error rate per FTB statistics.
- Do have an officer (not a preparer) sign Form 100-WE, because preparer signatures void the election.
- Don’t staple anything inside the OCR barcode zones, because staples physically jam the scanner.
- Don’t round to thousands; California requires whole-dollar entries, not abbreviations.
- Don’t forget the $800 minimum even in a loss year (after year 1), because the FTB will assess it with penalties.
- Don’t assume federal extensions extend California; California’s extension is automatic but separate.
- Don’t combine multiple unitary groups on one return; each combined group files its own Form 100W.
- Don’t ignore the Schedule R-7 election if filing a group return, because without it each member must file separately.
Pros and Cons of Filing on Your Own vs. With a CPA
- Pro (DIY): Saves $5,000–$25,000 in CPA fees for a simple single-entity filer, because the form is mechanically straightforward.
- Pro (DIY): Forces in-house staff to learn California rules, because hands-on filing builds institutional knowledge.
- Pro (DIY): Faster turnaround for late-filed extensions, because no third-party scheduling is involved.
- Pro (DIY): Direct control over Schedule R apportionment positions, because management chooses the sourcing methodology.
- Pro (DIY): Cheaper amendments, because you don’t pay a CPA to redo work.
- Con (DIY): Schedule H, Schedule P, and Schedule R are technical, because they require detailed knowledge of R&TC sections.
- Con (DIY): A botched Form 100-WE voids 7 years of election planning, because the election is irrevocable mid-period.
- Con (DIY): California audits are aggressive, because the FTB has more apportionment auditors per filer than any other state.
- Con (DIY): Software costs ($2,000–$8,000/year) often equal small-firm CPA fees, because corporate tax software is expensive.
- Con (DIY): Personal liability for officers who sign incorrect returns, because California pursues responsible-officer penalties under R&TC §19173.
Form 100 vs. Form 100W: Side-by-Side
| Feature | Form 100 / Form 100W |
|---|---|
| Filer | All C corps / Water’s-edge electors only |
| Income scope | Worldwide unitary / U.S. + partial CFCs |
| Election form | None / Form 100-WE required |
| Election period | N/A / 84 months |
| Dividend deduction | Schedule H / Schedule H (100W) |
| Tax rate | 8.84% / 8.84% (10.84% banks) |
| Due date | 4th month, 15th day / Same |
| Extension | Automatic to month 11 / Same |
| Minimum tax | $800 / $800 |
| Apportionment | Single-sales / Single-sales |
Worldwide vs. Water’s-Edge Reporting: Side-by-Side
| Feature | Worldwide / Water’s-Edge |
|---|---|
| Foreign affiliates | All included / Excluded (with partial CFC inclusion) |
| Statute | R&TC §25101 / R&TC §25110, §25113 |
| Best for | Foreign losses / Foreign profits |
| Election needed | No / Yes (Form 100-WE) |
| Subpart F income | Already in worldwide / Partially included |
| GILTI | Already in worldwide / Partially included via Schedule R |
| Term | Open-ended / 84 months |
| Termination | N/A / Letter under §25113(c) |
FAQs
Is Form 100W required for every California C corporation with a foreign subsidiary?
No. Form 100W is only required for C corporations that have made a valid water’s-edge election under R&TC §25113. Without that election, the corporation files Form 100 on a worldwide combined basis.
Is the $800 minimum franchise tax owed in a loss year?
Yes. Every California C corporation owes the $800 minimum franchise tax in any year it is doing business in California, except the first taxable year of existence under R&TC §23153.
Is Form 100-WE needed every year?
No. Form 100-WE is filed only once at the start of the 7-year election period, and stays in effect for 84 months unless terminated under R&TC §25113(c).
Do I write the California corporation number with dashes in the header box?
No. Enter the 7-digit California corporation number with no dashes, no spaces, and no leading zeros — for example, 2345678, not 02-345-678.
Do I check Question D Yes if I’m in year 5 of my election?
Yes. Check Question D Yes on every Form 100W filed during the 84-month election period, even though Form 100-WE is only attached the first year.
Does the FEIN go in Box 4 with dashes?
Yes. Enter the FEIN as XX-XXXXXXX with the standard hyphen after the second digit; the OCR scanner expects this format.
Is bonus depreciation allowed on Form 100W?
No. California does not conform to federal bonus depreciation under IRC §168(k), so add the federal bonus back on Schedule F and depreciate using California rules on Form 3885.
Can I e-file Form 100W?
Yes. Approved tax software supports MeF e-filing of Form 100W, Schedule H, Schedule P, and Form 100-WE per the FTB business e-file forms list.
Is the California NOL deduction allowed in 2025?
No. California suspends the NOL deduction in 2024 and 2025 for taxpayers with $1 million or more of California net business income, per the 2025 booklet.
Is the water’s-edge election irrevocable?
No. It can be terminated under R&TC §25113(c) by filing a written termination request, but only after the original 84-month period has run.
Does throwback apply to water’s-edge filers?
No. California does not apply the throwback rule to water’s-edge filers under R&TC §25135, so non-California sales of nowhere-taxed goods do not get pulled back.
Do banks file Form 100W?
Yes. Banks and financial corporations that have made a water’s-edge election file Form 100W and pay tax at the higher 10.84% rate under R&TC §23186.
Do I attach federal Form 1120?
Yes. A complete copy of federal Form 1120, with all schedules and statements, must be attached to every Form 100W under California Code of Regulations §25137.
Does the FTB accept electronic signatures on Form 100-WE?
Yes. The FTB accepts electronic signatures on Form 100-WE when transmitted via approved MeF software, per the FTB e-file business forms guidance.
Related reading
- How to Fill Out California Form 100-ES (w/Examples) + FAQs
- How to Fill Out California Form 100 (w/Examples) + FAQs
- How to Fill Out California Form 100-X (w/Examples) + FAQs
- How to Fill Out California Form 100S (w/Examples) + FAQs
- How to Fill Out California Form 565 (w/Examples) + FAQs
- How to Fill Out California Form 568 (w/Examples) + FAQs