What makes a water's edge election valid when the return and the election disagree?
Edvin Givargis Published 6 minute read
The short answer
A California water's edge election has two components, and both live on the same return: an election made in the prescribed form and manner on a timely filed original return, and a tax computation consistent with filing on a water's edge basis (Rev. and Tax. Code section 25113; Cal. Code Regs., tit. 18, section 25113). When the return does both, the election is valid for eighty-four months. The hard cases are the mismatches, and they run in both directions. A group that attaches the election form but computes its tax on a worldwide combined basis will face the Franchise Tax Board's position that the election is invalid, because the statute asks for a water's edge computation, not just a water's edge form. A group that computes on a water's edge basis but never makes the election in form faces the opposite argument, that no election exists and the worldwide default applies. Neither mismatch is automatically fatal, because the regulation tempers the statute with an objective evidence standard, deemed election rules, and treatment of certain corrective filings as the original return. What is absolutely fatal is timing: an election can only be made on a timely filed original return, and a late return or a later amended return cannot make one.
How the election is supposed to be made
The clean case is mechanical. Every member of the self-assessed combined reporting group that is subject to California tax elects, on a timely filed original return for the first water's edge year, by filing the water's edge return form, Form 100W, with the election form, Form 100-WE, attached, and by computing the tax on a water's edge basis. The election is a single group-level act executed member by member, it binds the group for an eighty-four month period, and termination before the period runs requires Franchise Tax Board consent on a showing of good cause, with re-election after a termination itself subject to consent rules. The commitment period, and what happens to it when electing groups merge, reorganize, or acquire nonelecting members, is its own subject, covered in the companion article on the water's edge election and reorganizations; this article is about whether an election came into existence at all.
Mismatch one: the form is there, the computation is not
The first failure pattern is the group that attaches Form 100-WE to a timely original return and then, through preparer error, a software configuration, or a late change of heart imperfectly executed, computes the tax on a worldwide combined basis. The Franchise Tax Board's position in this pattern is that the election is invalid: the statute conditions the election on the tax being computed in a manner consistent with a water's edge election, and a worldwide computation is the opposite of that. The stakes are usually large in one direction or the other, because the group either wanted the election, and now faces worldwide combination for years it planned around water's edge, or regrets it, and would happily accept the Board's invalidity position if it points the other way.
The counterweight is that the regulation does not make consistency a single-factor death test. It directs the Board to consider objective evidence of what the taxpayer did and intended, and it contemplates that timely filings which supplement a previously filed return can be treated as the original return for election purposes where the objective evidence supports the conclusion that a water's edge election was intended. A group that catches the computational error inside its filing window, extension included, and supplements with a corrected water's edge computation has a genuinely strong position that the corrected filing is the original return and the election stands. A group that discovers the mismatch years later, on audit, is arguing intent from a return whose numbers said worldwide, and should expect the Board to read the return against it, in whichever direction the revenue runs.
Mismatch two: the computation is there, the form is not
The mirror image is the group that files Form 100W and computes everything on a water's edge basis but fails to make the election in form, a missing Form 100-WE, a member that never signed, an attachment dropped in assembly. Here the regulation is more forgiving than the folklore suggests, in two distinct ways. First, the form itself is the standard manner but not the only one: the Board may accept other objective evidence of the election, including statements attached to the return and substantially completed water's edge forms, so a return that is water's edge in substance from cover to cover is itself evidence that the election was made. Second, the deemed election rules pick up group members who never elected on their own: a taxpayer whose income and apportionment factors were included in the water's edge combined report of an electing parent is deemed to have elected, and a notification signed by an officer or agent with authority to bind the member can supply the member-level election. These rules exist precisely so that a group-wide election does not fail because one subsidiary's paperwork did.
What the forgiveness never reaches is the calendar. Every path to a valid election runs through a timely filed original return. A group that missed the filing deadline has no election for that year no matter what the return says, an amended return filed after the original cannot create an election the original did not make, and the practical consequence is that the water's edge decision must be final, executed, and internally consistent by the extended due date of the first year's return, or deferred to a later year.
Practice notes
The failure patterns here are process failures, and the fixes are checklist items. First, the election package should be assembled and reviewed as a unit: Form 100W, Form 100-WE signed for every member subject to tax, and a computation that is water's edge from the combined report through the tax line, verified against each other before filing, because the two mismatch patterns above are both one unreviewed detail away from any first-year filing. Second, the supplemental-filing window is the cheap cure: any inconsistency discovered before the extended due date should be corrected by a superseding filing while the correction can still claim to be the original return, and the objective evidence of intent, board minutes, election workpapers, the engagement correspondence, should be preserved with the file rather than reconstructed later. Third, groups inheriting a return history, through acquisition or a preparer change, should confirm what the election record actually is before assuming the group's status; a member deemed elected through a parent's report, or an election resting on objective evidence rather than a clean form, is valid but worth documenting affirmatively before an audit asks. And where the Board asserts invalidity of a form-plus-worldwide-computation filing, the position should be tested rather than conceded, in either direction: the regulation's objective evidence framework cuts for whoever the contemporaneous record supports, and the same rules that rescue an intended election can defeat an accidental one.
This article states the law as of September 15, 2026
Statutes, rates, thresholds, and agency practice change, and a different set of facts can change the answer. Before acting on anything discussed above, contact G&G State Tax Group to confirm what has changed since this was written and how the rules apply to a specific situation.
G&G State Tax Group, LLC is a state and local tax advisory firm. The firm provides state and local tax consulting and representation in state and local tax controversies. G&G does not prepare or file tax returns, perform attest services, or provide bookkeeping, and is not a CPA firm.