In order to file federal tax returns, businesses are generally required to have an Employer Identification Number (EIN). This number is used to uniquely identify each business entity. You can apply for an EIN on the IRS website, through a free, interview style process. Follow the link below, and then click 'APPLY ONLINE NOW' at the bottom of the page to apply for an EIN. This link also provides further information about EINs, and the process of obtaining one for your business.