FEIN No. - Is it really needed?

[Rose M.]

Wondering - I have an LLC (single member) in state of IL. I would like to start investing, buying properties, etc. and transact with my LLC. Do I apply for an FEIN no. or do I just use my SS? From what I have read in the forums, I should keep my expenses, etc. separate so I want to open a Business checking account for my LLC and I am not sure if I should obtain the FEIN no. or just use my SS. I think I am getting confused since I was always told to purchase/transact with my LLC (not my name) for protection purposes and so that the "corporate veil could not be pierced" for legal matters. With this said, if I just use my SS, isn't this defeating the purpose? Thank you. Rose