What happens after an S corporation files a California refund claim?

The substance: re-sourcing receipts, and what it does to each shareholder

For taxable years under California's market-based regime, receipts from sales other than tangible personal property are assigned to California only to the extent the customer receives the benefit, or uses the intangible or licensed property, in California (Revenue and Taxation Code section 25136(a)). For a software business selling nationally, the difference between the old habit, sourcing everything to the home state where the code was written, and the market rule can be most of the sales factor, and the amended returns, filed on Form 100X for the S corporation, implement the correction. Characterization comes first, in the claim years no less than going forward: license fees for software replication and installation rights are receipts from licenses of intangible property rather than sales of tangible personal property (Microsoft Corp. v. Franchise Tax Board (2012) 212 Cal.App.4th 78), the pre-2026 regulation sources intangible licenses under its own assignment rules rather than the services cascade, and FTB Legal Ruling 2022-01 (March 25, 2022), which revoked the Chief Counsel Rulings that preceded it, is the Franchise Tax Board's controlling guidance for open-year service receipts, placing the benefit of a service directed at the customer's own customers at those customers' locations. For service receipts from business customers, the pre-2026 regulation then runs a cascade of its own, and billing address is not a reasonable-approximation method within it: the location is fixed first by the contract or the taxpayer's books and records, notwithstanding the billing address, a presumption that either the taxpayer or the Franchise Tax Board may overcome by a preponderance of the evidence; then by reasonable approximation; then by the location from which the customer placed the order; and only at the end by the customer's billing address (former Cal. Code Regs., tit. 18, section 25136-2(c)(2)). A claim rebuilt on billing address alone therefore starts at the bottom of the hierarchy the auditor will apply, which is why the customer-location workpapers, and the data behind them, are the heart of the claim.

The shareholder cascade then splits along residence lines, though less cleanly than the folklore has it. A nonresident shareholder is taxed by California only on California-source income, and the pass-through's apportionment is what sources it, so the amended K-1 that carries a collapsed California-source number is the nonresident's entire case; the shareholder files a personal refund claim on the strength of it, and the dollar movement at a top-bracket individual rate routinely dwarfs the entity's own 1.5 percent refund. A resident shareholder is taxed by California on all income regardless of source, so re-sourcing the entity's receipts does not change the resident's California taxable income, but it can change the resident's credit for net income taxes paid to other states, because that credit is allowed only for tax on income derived from sources within the other state, and the statute determines that source by applying California's nonresident sourcing rules (Revenue and Taxation Code section 18001(a)(1), (c)). When the corrected apportionment assigns more of the entity's income outside California, more of the resident's share can qualify for the credit, subject to the statute's proportional limitation (section 18001(a)(3)), so resident returns can change too. Residents who paid tax to other states on the same income belong in the limitations table alongside the nonresidents, and a claim based on tax paid to another state may also be filed within one year of that payment if that period ends later (Revenue and Taxation Code section 19311.5). One more layer applies where the S corporation elected the pass-through entity elective tax for a claim year. The Franchise Tax Board's published guidance on the election provides that a change in income requires the entity to revise its qualified net income on the amended return, permits the entity to claim a refund of the resulting elective tax overpayment, and requires each affected shareholder to revise the elective tax credit on an amended return, so a market-sourcing claim re-prices the elective tax and the consenting shareholders' credits along with everything else.

The procedure: deadlines first, then the audit the claim invites

The limitations analysis belongs at the top of the claim memo, in a table, entity and each shareholder, because the periods interact but do not merge. Each taxpayer's claim must be filed within its own window, the shareholder claims cannot be perfected until the entity's amended K-1s exist, and the schedule therefore runs backward from the earliest shareholder deadline, not forward from when the entity work happens to finish. Where a deadline is close, a protective claim, filed on the available numbers and perfected later, preserves the year; discovering the shareholder deadline after polishing the entity claim is the unforced error this area exists to prevent. Then comes the examination. A refund claim audit inverts the usual posture: the taxpayer asserted the facts, so the taxpayer proves them, and for a sourcing claim that means producing the customer-location analysis, the revenue detail behind it, and the tie-out from the workpapers to the amended returns, years after the returns were filed, often after the people who built them have moved on. The support should be assembled for that future on the day the claim is filed: the sourcing workpapers, the data extracts, the methodology memo explaining the proxy used and why it is reasonable, and the deliverable set, archived where the eventual responder can find them, because reconstructing a claim's support from scattered drives while the auditor waits is how strong claims develop weak records. The audit can be expected to test both direction and degree, whether market sourcing applies and whether the customer-location data supports the split claimed, and the state can be expected to look for offsets in the same years, since the Franchise Tax Board may retain amounts already paid that do not exceed the tax properly due for the year, even after the period to assess additional tax has closed (Lewis v. Reynolds (1932) 284 U.S. 281, 283; Owens-Corning Fiberglas Corp. v. State Bd. of Equalization (1974) 39 Cal.App.3d 532, 536; see Jibilian v. Franchise Tax Board (2006) 136 Cal.App.4th 862). Interest runs on what is ultimately refunded, at the overpayment rate under Revenue and Taxation Code section 19521, which for the corporation's own refund is capped at the lesser of 5 percent or the 13-week Treasury bill rate and for individual shareholders equals the underpayment rate; it rewards patience but never substitutes for it.

The claim also has a formal endgame, and the calendar keeps running through it. If the Franchise Tax Board denies the claim, its action becomes final 90 days after the notice of action is mailed unless the taxpayer appeals in writing to the Office of Tax Appeals within that period (Revenue and Taxation Code section 19324(a)). If no notice of action is mailed within six months after the claim is filed, the taxpayer may treat the claim as denied and appeal, or bring a refund action in superior court before the notice is mailed (sections 19331, 19385). A refund action must be commenced by the latest of four years from the last date prescribed for filing the return, one year from payment, or 90 days after the notice of action or a final determination on appeal (section 19384). A claim strategy that has survived the audit can still lose to this calendar, which is why the 90-day and six-month markers belong on the same deadline table as the limitations periods.

Practice notes

The checklist: limitations table for entity and every shareholder before substantive work begins, with protective claims for any window inside the working horizon; residency sort of the shareholder roster, where nonresidents drive the deadlines and amendments, and residents with other-state tax get a credit recomputation and a deadline of their own under Revenue and Taxation Code sections 18001 and 19311.5; customer-location workpapers built to audit standard at filing, with the methodology memo attached to the claim support rather than implied by it; and the archive discipline, deliverables, data, and tie-outs stored against the examination that should be assumed. Under audit, the burden posture shapes the tone: the sound approach is affirmative production, support organized around the claim's own logic, and a state offset review treated as expected rather than aggressive. The prospective fix belongs alongside the retrospective one, because a company that needed to amend three years of sourcing needs its current-year apportionment rebuilt for the new era rather than carried forward unchanged: for taxable years beginning on or after January 1, 2026, amended Regulation 25136-2 governs, and the first question is characterization: license fees are assigned where the licensed software is used, while receipts the regulation treats as services follow a cascade that looks first to the contracts or books and records kept in the normal course of business, then to other available information, then to a reasonable approximation, and only then to the customer's billing address, with the presumptions the cascade creates overcome by a preponderance of the evidence, offered by either the taxpayer or the Franchise Tax Board. For business customers that ordering is continuity rather than novelty, since billing address sat at the end of the pre-2026 business-customer cascade with the same two-way rebuttal; what the amendment changed for services was folding the individual-customer rules, where billing address had been the starting presumption, into the single cascade. The amendment also added a mandatory billing-address rule: a taxpayer providing a listed professional service, a category that includes business advisory and technology consulting services, to more than 250 customers assigns those receipts to the customer's billing address, except for any customer providing more than 5 percent of the receipts from that service (Cal. Code Regs., tit. 18, section 25136-2(c)(3)). And the rebuilt method, once chosen, is sticky: a taxpayer that has used a reasonable-approximation method must continue to use that method in subsequent taxable years, and may not change it without the permission of the Franchise Tax Board, on notice in the form the FTB prescribes (section 25136-2(i)(2)(C)). The same customer data supports both eras, but the go-forward method has to be rebuilt on that hierarchy rather than carried forward on a billing-address habit, because a method that starts where the regulation ends is a method the next examination will unwind, which puts the company back in the refund-claim posture with fewer open years to save. G&G State Tax Group provides market-based sourcing refund claims and claim representation alongside its state and local tax practice.