If you are a small business./self-employed, you can use your SSN or get an EIN for yourself from the IRS. You must have an EIN if you pay employees, but even if you are an independent contractor with no employees, you might want an EIN so that you don't have to give your personal SSN to your clients and vendors.
If you have more than one business, each business needs a different EIN. Also, if you change the type of business (such as from a sole proprietorship to a partnership) you need a new EIN.
Get an EIN here,
https://www.irs.gov/businesses/small-businesses-self-employed/apply-for-an-employer-identification-n...
