Corporate Fair Share Tax Act - Amends the Internal Revenue Code to limit the tax deduction of the interest expense of a U.S. corporation that is a member of a financial reporting group (a group that prepares consolidated financial statements according to accepted accounting principles or international financial reporting standards) to: (1) the amount of interest on indebtedness of the corporation includible in the corporation's gross income for the taxable year plus its proportionate share of the group's net interest expense in the taxable year; or (2) 10% of the corporation's adjusted taxable income, if the corporation fails to substantiate its proportionate share of interest expense. Exempts a corporation that is predominantly engaged in the active conduct of a banking, financing, or similar business or that has less than $5 million of net interest expense for the taxable year.