Actually, an EIN is a Federal Employer Identification Number. Generally speaking, Sole Proprietorships typically use their Social Security Number. If, however you incorporate, have employees, are a partnership and quite a few more situations, you obtain an EIN by completing and submitting IRS Form SS-4.

Actually, if you go to www.irs.gov and search under forms for SS-4, you'll find a .pdf version of the form that has an entire page titled "Do I Need an EIN"

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