Business opened DDA accounts under their name and EIN, years later the business was bought by another entity. New name and we assume new EIN. What is an acceptable time frame to allow them to provide new business documents? Also better scenarios: close current accounts and open new or name change current accounts?

If the entity was a corporation and it was sold by its owners to new ownership, there would not necessarily have been a change requiring a new EIN or, for that matter, new corporate filings (unless the state of incorporation requires new filings when ownership changes hands). The name change, though, suggests there may have been a winding down of the first business as it was absorbed by the new owners. Ask for the current owners to provide you a short history of what has happened, then decide if you need new documentation.

Thank you for the information John.