Such deduction shall not exceed the portion of the expenditure directly related to (or in the case of an expenditure described in subdivision (ii) of this subparagraph, the portion of the expenditure associated with) the active conduct of the taxpayer's trade or business.
An expenditure for entertainment in any such case is considered not to be directly related to the active conduct of the taxpayer's trade or business unless the taxpayer clearly establishes to the contrary.
Example. If an employer rewards the employee (and the employee's spouse) with an expense paid vacation trip, the expense is deductible by the employer (if otherwise allowable under section 162 and the regulations thereunder) to the extent the employer treats the expenses as compensation and as wages. On the other hand, if a taxpayer owns a yacht which the taxpayer uses for the entertainment of business customers, the portion of salary paid to employee members of the crew which is allocable to use of the yacht for entertainment purposes (even though treated on the taxpayer's tax return as compensation and treated as wages for withholding tax purposes) would not come within this exception since the members of the crew were not recipients of the entertainment. If an expenditure of a type described in this subdivision properly constitutes a dividend paid to a shareholder or if it constitutes unreasonable compensation paid to an employee, nothing in this exception prevents disallowance of the expenditure to the taxpayer under other provisions of the Internal Revenue Code.
26 C.F.R. §1.274-2