The Klaassens (plaintiffs) had ten children and an adjusted gross income of $83,056.42. On their federal income tax return the Klaassens claimed deductions for their state and local taxes, medical expenses, and 12 personal exemptions. The Klaassens resulting tax liability was $5,111.00. The Internal Revenue Service (IRS) (defendant) audited the Klaassens, and found that they owed an alternative minimum tax (AMT) of $1,085.43. The Klaassens appealed, claiming that the AMT was meant to apply only to wealthy people who claimed tax preference items under 26 U.S.C. § 57. The Klaassens did not challenge the IRS’s calculation of the AMT, only its application. The United States Tax Court affirmed the IRS’s interpretation. The Klaassens appealed.