I respectfully disagree with Andrea’s choice, although he is not wrong. It is true that “costituzione” can be translated as establishment, but Webster’s New Universal Unabridged Dictionary (second edition) offers establishment as an equivalent meaning for domiciliation. To maintain the differentiation of meaning in the translation, it would be better to say “constitution”.

The best word to describe the setting up of a new company is either formation or incorporation: in fact, the brochure you are translating is probably for a "company formation agent" involved in offering offshore companies in tax havens.