Business Mileage Conundrum

Pennywise

I suspect your employer is thinking about some old rules. There was a short period of time where HMRC tried to insist that "triangulation" rules applied for business travel, which indeed was all about deducting your normal commuting mileage from your business journeys. I can't remember when they were trying this, but it got shot down pretty quickly. There was, however, a small period of time when it was big news, so that's what he may be thinking about if it affected him at that time.