Here are some resources for your reference:
https://www.irs.gov/businesses/small-businesses-self-employed/do-you-need-a-new-ein
https://sa.www4.irs.gov/modiein/individual/help/help-toc.jsp
https://sa.www4.irs.gov/modiein/individual/help/keyword.jsp?question=Do%20I%20need%20a%20new%20EIN?
