Series LLCs: one filing, many walls, and almost no court has tested any of them

The pitch is irresistible. Instead of forming ten LLCs for ten rental properties, and paying ten filing fees and ten annual reports, you form one series LLC. Inside it you create ten series, each holding one property, each walled off from the others. A tenant sues over the property in series three, and only series three’s assets are exposed. One filing, one fee, ten walls.

About two dozen states now sell this structure, and Florida became the newest two days ago, its series law taking effect July 1, 2026. The structure is real, the savings are real, and for the right owner it works. What the pitch leaves out is what the walls are made of.

Think of a series LLC as a ship built with watertight compartments. Flood one compartment and the ship stays afloat. The design is sound. The problem is that the bulkheads were welded by a law barely twenty-five years old, almost no court has ever pressure-tested them, and the moment the ship sails into a state without series laws, nobody can tell you whether the compartments exist at all.

What a series LLC is

A series LLC has two layers. The parent LLC files with the state, holds the registered agent, and exists on the public record. Beneath it, the owners create individual series, each of which can have its own assets, its own bank account, its own members, and its own business. In most states a new series takes nothing more than an amendment to the operating agreement; Illinois and a few others require a public filing per series.

The promise is the internal shield: the debts of one series cannot reach the assets of another series or of the parent. That sentence is the entire product. Everything on this page is about whether the sentence holds.

The walls demand the same work as separate companies

Start with the piece that is fully within your control, because most series LLCs fail here before any court gets a chance to.

The shield holds only if each series actually lives separately: its own bank account, its own books, assets titled in its name, contracts signed in its name. Mix the money between series and you have done to the internal walls exactly what commingling does to a regular LLC’s wall, handed the other side the argument that the separation was decoration. Piercing the veil explains that attack; a series structure multiplies the places it can land.

Notice what this does to the sales pitch. The filing fees drop, but the bookkeeping burden of ten series equals the burden of ten LLCs. The discount is on paperwork, never on discipline. An owner who will not keep ten sets of books should not own ten of anything walled.

Problem one: the walls are untested

The series LLC’s central promise has almost no case law behind it. Delaware invented the structure in 1996, real estate investors have piled in for two decades, and the body of court decisions actually enforcing the wall between series when a creditor attacks it remains close to empty.

That is not proof the walls fail. It is proof nobody knows. Your ordinary LLC’s liability shield rests on more than a century of courts honoring it. The series shield rests on statutory text plus hope. A structure whose whole value is what happens in the worst moment should trouble you when the worst moment has barely ever been litigated.

Problem two: the walls may not travel

Form a Texas series LLC and keep everything in Texas, and Texas law governs. Put one of the properties in a state with no series statute, and the question becomes whether that state’s courts will honor internal walls their own legislature never created. Where your LLC actually lives explains why the paperwork state loses that fight more often than people expect.

Roughly thirty states have no series law, and most of them have no procedure for a series to register, no rule for how their courts should treat one, and no answer to the only question that matters. A court in one of those states facing an out-of-state series LLC can simply treat the whole ship as one hull, every compartment open to every claim.

Arizona put the danger in writing, and it is worth quoting as a warning label: its statute lets a foreign series register, then declares that the series is liable for the debts of the parent and of every other series. Registration granted, protection deleted. Every multi-state series plan needs to be checked against language like that, state by state, before the first deed transfers.

Problem three: bankruptcy is a black hole

Nobody knows whether a single series can file bankruptcy on its own, or whether one series going under drags the parent and the siblings into the case. The federal Bankruptcy Code was written without series in mind, the courts have not settled it, and the uniform law meant to fix it has reached only a handful of states.

The single-member LLCs page shows what federal bankruptcy courts do to state-law protections they consider beside the point. A structure with an unknown bankruptcy outcome is carrying its biggest risk exactly where risks get decided fastest.

Problem four: the tax answer is a shrug

The IRS proposed rules in 2010 treating each series as its own taxpayer. Sixteen years later the rules have never been finalized, so federal treatment runs on proposed regulations and professional judgment. Most practitioners treat each series as a separate entity for tax purposes, and most of the time that works, but you are building on an agency’s unfinished sentence.

California turns the shrug into a bill. It will not let you form a series LLC, but it recognizes foreign ones, and its Franchise Tax Board treats every series doing business in California as its own LLC owing its own $800 a year. Five series working in California owe $4,000 annually before earning a dollar, which quietly deletes the one-cheap-filing pitch for anyone the state can reach.

Where the states land

Three groups, and the full 51-state table is coming to this page.

States that authorize formation, about two dozen: Delaware wrote the original model, Illinois built the version requiring per-series filings, and Texas, Nevada, Wyoming, Utah, Tennessee, and Oklahoma run strong statutes of their own. A newer wave has adopted the Uniform Protected Series Act, which gives series clearer legal personhood and stricter guardrails; Arkansas, Virginia, Iowa, and Nebraska are in that group. Florida joined the authorizing states on July 1, 2026 with a UPSA-based law.

States that recognize but will not form: California is the loud example, taking $800 per series for the privilege. Georgia registers foreign series without offering domestic ones.

States that are silent or hostile: the remainder, where the travel problem lives and where the Arizona-style fine print hides.

Who should actually use one

The honest use case is narrow and real. An investor whose properties all sit in one strong series state, who forms there, banks separately per series, keeps clean books per series, and never lets the structure cross into a silent state, gets most of the theoretical benefit at genuine savings. Texas investors with Texas portfolios are the textbook case, and Florida investors just received the same option.

Everyone else is trading a known, proven tool for an unproven one to save filing fees. Ten separate LLCs cost more per year, and every one of them carries a shield courts have honored for a century, walls that exist in all fifty states, a settled tax answer, and a known bankruptcy outcome. That is what the extra fees buy. Sophisticated advisors keep recommending separate LLCs for exactly this reason, and on this site the position is the same: the series LLC is a bet that untested law will hold on the day you need it most, and the premium you save is small against the size of the bet.

The bottom line

A series LLC in the right state, holding in-state assets, run with real per-series discipline, is a legitimate cost saver for a portfolio owner. Taken across state lines, run with casual books, or holding anything you cannot afford to lose in an unlitigated structure, it is a discount on the one product you never want bought at a discount. When the walls matter, pay for the proven ones.