The SS4 is the IRS form required to obtain an EIN (Employer Identification Number, frequently called a Tax ID number). The EIN/Tax ID number can be thought of as a Social Security Number for your business. It is usually required to open a bank account in the name of the business and to properly pay and account for any wage/payroll employees of your company. QuickCorps will obtain your federal EIN electronically and have it back to you via email within one business day.