A Series LLC is a special form of a Limited liability company that provides extra protection for personal assets comprised of multiple business entities. A limited liability company (denoted by L.L.C. or LLC in the US) is a legal form of business company in the United States offering limited liability to its owners. ...

Many form an LLC in order to protect personal assets from a legal claim relating to their real estate investment or business liabilities.[1] Additional liability protection may be gained by properly forming and maintaining a separate LLC to hold each property or business entity. By forming a separate LLC to own and hold each legally titled separate property or business entity, theoretically only the assets owned by a specific LLC would be subject to claims or lawsuits arising against that LLC. However there are costs and administrative burdens associated with properly forming, qualifying and maintaining each separate LLC. Another option may be to form a Series LLC[2], a.k.a. the "cell" LLC, if permitted under applicable laws. Although each cell of a Series LLC can own distinct assets, incur separate liabilities, and have different managers and members, a Series LLC pays one filing fee and files one income tax return each year, if each series member is also a founding member of the LLC. When non-founding members are added to a newly created cell within the Series LLC, that new cell should file a separate partnership tax return for that cell. Furthermore, liability incurred by one unit does not cross over and jeopardize assets titled in other subsidiary units of the same Series LLC.[3] Also, if a business owns real estate used in its operations, a Series LLC may avoid sales tax due on rent paid by the operating series to the real estate series.[4] A Series LLC has been described as a master LLC that has separate divisions, which is similar to an S corporation with Q-subs.

The procedure for adding and deleting series is uncomplicated. Additional series can be added by simply amending the Series' “limited liability company agreement” (equivalent to an operating agreement for other LLCs). Under Delaware law, any particular series may be dissolved by 2/3rd's approval of the ownership interests, or a simple majority if provided for in the operating agreement.

This method of liability segregation was first called the "Delaware Series LLC" because it was first approved in Delaware[5]. As of April 2005, Iowa and Oklahoma already had passed similar acts. Illinois followed suit in August of 2005 [6]. The series LLC is not more widely used as a liability segregation technique because its tax treatment has not been fully resolved and because its effectiveness has not been tested judicially. Currently, the federal tax standards for a Series LLC with multiple members remains unclear. Some speculate that single entity federal tax treatment will require highly correlated assets, members and managers (particularly the last two). There is further speculation that California will only tax income from those series conducting business in California. Other states may follow. However, as of April 2006, The California Franchise Tax Board has determined that each Series of a Delaware Series LLC must report and pay taxes as a separate entity in California.[7] Also, since the asset protection and planning advantages of the Series LLC have not been thoroughly challenged in asset protection cases, they remain theoretical, and unproven. To minimize the chances of one series being held liable for another’s liabilities, the owners of a Delaware Series LLC should do the following[8]:

• Keep the assets and operations of each series separate from the other series. Each asset should be owned solely by one series. In other words, two or more series should not be co-owners of the same property.
• Make sure each series is adequately capitalized.
• Have each series file a fictitious business name statement in each county where it owns property. Each series should have its own name and the filing should emphasize the ownership of that series, for example, “Abracadabra LLC, Blackacre Series only”. This is to put creditors on notice.
• All contracts, deeds, notes, etc. should be signed in the name of the series. Again, use something like “Abracadabra LLC, Blackacre Series only”.
• A separate bank account should be maintained for each series.
• Any loans between series should be properly documented.
• Any transactions between series should be conducted in an arms’-length manner at fair market prices using appraisals.