So how can the problem of corporate tax avoidance be tackled and the public's understanding of the issue improved?...The Fair Tax Mark will use a set of metrics to assess companies on their tax and transparency. Companies that score a minimum of 13 out of 20 will be awarded a Fair Tax Mark...Yet for some participants, defining what the "right amount of tax" is could be problematic...But if signing up to the Fair Tax Mark is voluntary, why would businesses choose to do so? [refers to Google, Facebook, Amazon, Starbucks, Thomas Reuters, Co-operative, Unity Trust Bank]