In the case of qualified tips received by an individual during any taxable year in the course of a trade or business (other than the trade or business of performing services as an employee) of such individual, such qualified tips shall be taken into account under subsection (a) only to the extent that the gross income for the taxpayer from such trade or business for such taxable year (including such qualified tips) exceeds the sum of the deductions (other than the deduction allowed under this section) allocable to the trade or business in which such qualified tips are received by the individual for such taxable year.