An important court case for the loss disallowance rule was Rite Aid Corp v.
An Internal Revenue Service rule implemented in 1991 to prevent a consolidated group - a business conglomerate filing a single tax return on behalf of its subsidiaries - from taking a tax deduction for losses on the sale of a subsidiary's stock. The IRS wanted to make sure corporations paid taxes on their capital gains and wanted to prevent them from claiming the same loss twice as a tax deduction - known as a duplicated loss.