An LLC is a business structure granted by state statute. For federal tax purposes, it is disregarded. All it does it protect (sometimes) an owner's personal assets from being seized in a lawsuit against the company. That's why it's called a Limited Liability Company. It does not make a passive activity active. Real estate professionals who meet the material participation tests file Sch C, not Sch E, and can claim home office. Your client's single rental property likely is a passive activity (unless it's a huge complex that he works on full time). In a nutshell, forming an LLC and putting property into it is a state classification and has nothing to do with federal taxation. To the IRS, it's still whatever type of business it is and all the usual rules apply.