That is a bit crazy if you are in the US. There is no ‘business Id’ just say you are a sole proprietorship, meaning the business is just you, no corporation structure or anything like that and you are dba, doing business as, and your name.

That is how you technically describe yourself when you are a business when you are a person.

Your tax id number would just be your social security number.

It’s legal to transact business as a person.