To be deductible from the earnings of an employment an expense must be incurred wholly and exclusively in the performance of the duties of the employment. The words "wholly" and "exclusively" prevent a deduction for expenditure that serves a dual purpose, a business purpose and a non-business purpose. The wholly and exclusively rule does not apply to travel expenses, see EIM31805.
An example of dual purpose expenditure is money spent on
ordinary clothing that is worn at work. Clothing that is worn both
in work and out of work obviously has a dual purpose and so no
deduction is allowed. However, even if the clothing is
only worn at work no deduction is allowed. This is
because at one and the same time the clothing has the purpose of
providing cover and comfort to the employee as well as the purpose
of being suitable for work, see
EIM31663.
You can allow a deduction for the whole or part of a single
expense that has a dual purpose in two circumstances:
Example EIM31665 deals with an expense that cannot be apportioned. Example EIM31617 deals with a benefits charge that can be apportioned.
