Bruce Voss and Charles Sophy (plaintiffs) were not married but owned a house together. For their 2006 and 2007 tax returns, Voss and Sophy each claimed a mortgage interest deduction under section 163(h)(3) of the Internal Revenue Code. Section 163(h)(3) placed a $1.1 million limit on the amount of home-related debt on which a taxpayer could claim a deduction. The IRS audited Voss and Sophy and determined that as co-owners of the house they were jointly subject to the $1.1 million limit. The IRS thus disallowed a portion of each of their claimed deductions. Voss and Sophy brought suit in tax court. The tax court affirmed the IRS’s determination. Voss and Sophy appealed. The IRS presented a 2009 memorandum from its Chief Counsel, which stated the debt limit applies on a per-residence basis.