Federal tax id and state tax id (UBI number)

[Elmo]

Hi, I have a question regarding the federal tax id and state tax id (UBI number) for doing business in the US. People need to obtain federal tax id number in order to open a business banking account and when they do telephone banking, usually the operator (in the bank) would verrify the caller's idenetity by confir the federal tax id number. So in other words, the federal tax id number shpuld not be given out to other people or else they can get access to our bank accounts (telephone banking). But I found that some of our manufacturers/suppliers/wholesalers ask us to give them the federal tax id number instead of the state tax number (UBI number) when we apply to be the dealer so I am wondering it's common for the manufacturers/suppliers/wholesalers to ask for other companies' federal tax id number? Isn't the state tax id number sufficient to prove that the business owner is operating a legtimate business? I am wondering how come some manufacturers/suppliers/wholesalers would ask for the federal tax id and is it legal for them to ask for that? Any help would be much appreciated. Thanks for your time.