You should not normally tax the same expenditure on
entertainment twice. That would be the result if neither the
employer nor employee was given a deduction for it (see
EIM32585).
But there are circumstances where a double disallowance will
arise. For example, an employee may be given a round sum
entertainment allowance which is used to entertain members of his
or her family who have no connection with the employer's business.
In that situation the employer will not get a deduction because of
Section 577 ICTA 1988 or Section 45 ITTOIA 2005. At the same time,
the employee will not be entitled to a deduction under 336 ITEPA
2003 because the expenditure is not incurred in the performance of
the duties.