Normally, if you work in single EU country as contractor, you are treated like its tax resident and you are required to register company there. (This at least apply to Germany in Poland, where you are tax resident, if you spend over a half of year each year on their territory).
But say, I'd work as contractor 4 months in Germany, 4 months in Poland and 4 months in Czech Republic. In none of that countries I'd spend more than the half of that year, so in neither of them I'm tax resident.
Does it mean, that I'm then free to choose in which EU country I'd register my company?
For example, can I register in country, where the tax regulations are the most attractive for me, say, in Luxembourg?