An elephant or a letter box?

Key points * A working legal definition. * HMRC's guidance and examples. * The difference between 'arm's length' and 'market value'. * Is an actual or hypothetical open market necessary? * Connected persons and international aspects.

THE TRADITIONAL ANSWER to the question 'what is the difference between an elephant and a letter box?' is 'I don't know'; to which the natural response is 'well there's no point in sending you out to post a letter …'. The point is that each item is in itself easy to describe but each is so radically different from the other that it is hard to summarise the points of difference. There are other common terms of which everyone has a general concept but which are not susceptible of a convenient definition. Among them is the concept of a transaction carried out 'at arm's length'. This concept as readers...