EIM32060 - Travel expenses: travel for necessary attendance: definitions: ordinary commuting: necessary journeys
Section 337 and 338 ITEPA 2003
An employee cannot turn what is really an ordinary commuting journey into a business journey simply by arranging a business appointment along the way. To get a deduction the employee must be able to show that the attendance at the particular place on that occasion was necessary, in the sense used in EIM31645, for the performance of the duties of that employment and was not just a matter of personal convenience.
Similarly, an employer cannot turn an ordinary commuting journey into a business journey by requiring the employee to stop off on the way to carry out business tasks such as making telephone calls, see EIM32270.