There is not a rule that requires it to be on every page of your site. Some pages, those promoting nondeposit products for example, shouldn't have it. Pages dedicated to loan products don't have to include it, either, but it doesn't hurt. I do like linking it to the FDIC site and specifically the bank ID section but it isn’t required. It helps customers interested in your bank find more information about you and in a way helps validate your existence.
Learn more about Andy Zavoina’s Don’t Forget Website Auditing webinar.