I do my own self assessment, but am not in the building trade. When completing the tax form on line there is a box stating do you want to complete expenses as a single sum or breakdown. If he selects breakdown you get all of the categories PPE , travelling, office expenses ( this is where I code my mobile) , training. etc. These each have a small guidance note to explain the category. At the end the expenses are summarised as one line, but the breakdown is still visible.