I have 15 years of IT experience and I am with a IT company for 10 years. Now I am moving to a big company and they are going to do back ground verification. My question here is, is that necessary to do a back ground verification for a person who is with a company for 10 years? Even if they verify, would they verify my previous employment or the recent company? What if the previous companies are shifted to a new place or acquire by some other companies or even closed?