When Airbnb established its international headquarters in Dublin in 2013, the online short-term lettings agency was not only looking for skilled English-speaking workers in a European time zone. It also set up a so-called double Irish structure, which the US Internal Revenue Service (IRS) is now insisting allowed the company to minimise its US tax liability unduly – by the equivalent of over €1 billion. Airbnb disagrees and the massive tax bill is now headed for a protracted fight similar to the one that has pitted the IRS against Facebook in the US Tax Court for several years. Little was…