IT probably depends on the laws of each country.
In the UK, branches of a company can sign contracts - it is certain people/job roles that have the authority to do this or not and the head office will set the limits of who and what type of contract. Branch managers usually have a certain amount of authority. It wouldn't be very workable if a company with, say, 1000 branches over the UK, had to refer every tiny decision back to the head office, even just to arrange a local office cleaning contract for example.