The federal Employer identification Number i.e. EIN is a nine-digit unique number assigned to business by IRS for tax filing and reporting purposes. IRS uses this nine-digit unique EIN so as to identify the taxpayer. EIN is used by business entities or organization such as corporation or limited liability companies so as to file tax return. However, most of sole proprietors do not need to get an EIN and can use their Social Security Number instead. ph no (919) 504-6664