Can separate companies belonging to a corporation be processors? Will they be separate controllers?

ANSWER

Under the GDPR, each company is treated as a separate entity. The GDPR does not provide for exceptions that would allow related companies to be treated differently from companies that are independent of each other. For this reason, independent companies, when they wish to cooperate in a manner that has the characteristics of entrustment of data processing, e.g. one company commissions another to maintain HR documentation, may conclude a data processing agreement. In other situations, they may be independent controllers, e.g. each company is an independent controller in relation to its own employees.