A Delaware Series LLC is a single limited liability company, formed under 6 Del. C. § 18-215, that can hold any number of internal series, each with its own assets, debts, members, and liability shield. The master LLC is the entity on file with the state; the series live beneath it. When the paperwork and the bookkeeping are done right, a creditor of one series cannot reach the assets of another series or of the master itself.
The structure is popular with real estate investors who want each property in its own liability bucket and with fund managers running distinct portfolios under one roof. Only about 21 states and Puerto Rico authorize series LLCs at all, and Delaware’s version is the oldest and most tested.
The Two Layers, and the Two Kinds of Series
Everything sits under a master LLC. That master is what you file with the Delaware Division of Corporations, and it carries the state-level identity for the whole structure. Each series underneath it can hold its own property, sign its own contracts, and have its own members and managers.
Delaware offers two forms of series, and the choice shapes cost and credibility:
- Protected series. Created inside the operating agreement with no separate state filing. Cheap and quiet, but with no public record, which makes life harder when a bank or title company wants proof the series exists.
- Registered series. Formed by filing a Certificate of Registered Series with the Secretary of State. It gets its own public record, its own certificate of good standing, and the kind of standalone identity lenders usually insist on.
Both forms get the same statutory liability partition. What differs is how the outside world can see and verify them.
Protected or Registered: Which One Fits
A protected series works when the owner controls everything and no outsider needs to confirm the series is a recognized entity. The classic example is an investor who owns several rental properties and wants each in its own liability bucket without the cost of forming five separate LLCs.
A registered series is the right pick when the series will borrow money, hold bank accounts under its own name, or sign contracts where the counterparty needs to verify the entity. Because a registered series has a public filing, it can produce its own good-standing certificate.
Cost is the trade-off. Each registered series costs $110 to file and carries a $75 annual tax on top of the master LLC’s $300 annual franchise tax. Protected series have no filing fee and no separate annual tax. For a structure with dozens of series, the math pulls hard toward protected unless outside parties need the verification.
What to Have Ready Before Filing
Four pieces need to be in place before anything goes to the state.
- A name for the master LLC. It must be unique and comply with 6 Del. C. § 18-102. Every registered series name has to begin with the master LLC’s full name, so a short, clean master name saves work down the line.
- A Delaware registered agent. Every Delaware LLC must have one, with a physical office in the state. The agent’s name and street address go on the certificate of formation. Professional agents generally charge $50 to $200 a year.
- An operating agreement. It has to authorize the creation of series. It should also lay out how each series will be managed, how assets and records will be kept separate, and who can create new series. The agreement stays internal, but it is the legal spine of the whole arrangement.
- Series notice language in the certificate. The certificate of formation must state that the liabilities of any series are enforceable only against that series’ assets. This is what turns on the statutory shield. Leave it out and Delaware treats the entity as a plain LLC with everything exposed.
The notice does not have to name any specific series or use any magic word. It just has to put the public on notice that liability is partitioned.
Filing and Fees
The certificate of formation goes to the Delaware Division of Corporations. Most people file through the state’s eCorp Business Services portal; mail and in-person filing at the Dover office also work. The fee is $110.
For each registered series you want, file a separate Certificate of Registered Series. That filing also costs $110. The only required contents are the master LLC’s name and the series’ name, though you can add more.
Standard processing runs several business days. Delaware offers expedited tiers for an extra fee, ranging from next-day service for as little as $50 up to one-hour service at $1,000, with cutoffs that depend on the tier. Once approved, you get back a stamped copy of the certificate, which is your proof the entity exists.
Annual Taxes and Deadlines
Every Delaware LLC, including a Series LLC, owes a $300 annual franchise tax due June 1. Miss the date and the penalty is $200 plus 1.5 percent monthly interest on the balance.
Each registered series owes its own $75 annual tax, also due June 1. The late penalty on a registered series is $50 plus the same 1.5 percent monthly interest. A registered series that falls out of good standing can derail bank and lender transactions that depend on verifying its status.
Protected series owe no separate annual tax. A master LLC with ten registered series pays $1,050 a year to Delaware ($300 plus $750); the same structure using protected series pays $300. Delaware does not require LLCs to file annual reports, so the recurring compliance load is lighter than in many states.
Keeping the Liability Shield Intact
The statute grants the shield; your bookkeeping keeps it. This is where Series LLCs most often fail in practice.
Under 6 Del. C. § 18-215(b), each series must account for its own assets separately from the master LLC and every other series. The statute lets you do that by specific listing, category, type, percentage, formula, or any other method where each series’ assets are “objectively determinable.” The method is flexible; the separation itself has to be real and ongoing.
In day-to-day terms, that means each series should have its own bank account. Money should not move between series without documentation. Contracts should be signed in the name of the specific series, not the master LLC, so the counterparty knows which pool of assets stands behind the deal. Titles to real estate, vehicles, and equipment should name the owning series. Books should track each series’ income, expenses, and liabilities on their own.
If you commingle funds, pay one series’ debts out of another’s assets without a proper intercompany arrangement, or let the recordkeeping lapse, a court can collapse the walls. At that point creditors of any series can reach the assets of every other series and the master. The more series you run, the tighter the discipline has to be.
Federal Tax Treatment
The IRS has not finalized how Series LLCs are classified for federal tax. Proposed regulations issued in 2010 (REG-119921-09) would treat each series as a separate entity under the check-the-box rules, independently classified as a disregarded entity, partnership, or corporation. More than fifteen years later, those regulations are still proposed.
In practice, the IRS expects a series with its own members, its own books, and a distinct business purpose to get its own Employer Identification Number and file its own return (or appear as a separate disregarded entity on its owner’s return). A Series LLC where every series shares the same single owner and operates as one undifferentiated business may be able to file under a single EIN, but the absence of final guidance leaves real uncertainty.
The safer default for most owners is to treat each series as a separate entity, give each its own EIN, and keep the kind of separate financial records Delaware already requires for liability purposes. That lines up with both the proposed regulations and how the IRS actually behaves.
One federal filing you can set aside: as of March 2025, domestic entities are exempt from Beneficial Ownership Information reporting with FinCEN under the Corporate Transparency Act. An interim final rule limits reporting companies to entities formed under foreign law that have registered to do business in the United States. Neither the master LLC nor any series needs to file a BOI report.
Operating Outside Delaware
Forming in Delaware does not give you the right to do business elsewhere, and this is where the structure’s advantages can quietly disappear. If a series operates in another state, it generally has to register there as a foreign entity, and the reception depends on that state’s law.
Only about 21 states have series LLC statutes of their own. In states without one, a court may not recognize the partition between series. The judge could treat the whole structure as a single LLC for liability purposes, so a judgment against one series could reach the assets of every other series operating in that state.
Even states that recognize foreign series LLCs sometimes add requirements. Some demand that each individual series file its own foreign registration; some impose franchise taxes series by series. A handful go further and effectively eliminate the shield for foreign series operating within their borders.
The practical lesson is that a Delaware Series LLC performs best when its assets and activity stay in Delaware or in states with their own series statutes. Before putting a series to work in another state, check how that state treats foreign series LLCs. In some cases, a standalone LLC formed in the operating state gives you stronger protection than a Delaware series whose walls may not survive the border crossing.