The general rule for employees: expenses: necessarily incurred: an unavoidable expense may not be necessary
The fact that an expense may be unavoidable does not make it “necessary” for the purpose of section 336 ITEPA 2003. If it is to be deductible the expense must result from the requirements of the job and not from the personal circumstances of the individual.
For example, an employee with children may need to employ a child minder in order to go to work. The cost of the child minder is not deductible because it is not an expense that would be necessary for each and every employee; not all employees have children. The expense is unavoidable for that individual but is not deductible. If you need to know more about tax relief for costs of child care see EIM32445 and EIM21900 for the exemption for employer provided workplace nurseries.
This approach has been followed by the courts in several cases. For example, in Elderkin v Hindmarsh (60TC651), dealing with the accommodation expenses of a site based employee, Vinelott J. quoted from Viscount Cave on page 134 of Ricketts v Colquhoun (10TC118) to the effect that if a man:
“elects to live away from his work so that he must find board and lodging away from home, that is by his own choice, and not by reason of any necessity arising out of his employment.”