Obtaining an Employer Identification Number ("EIN") from the IRS is relatively quick and simple. A foreign business may apply for an EIN by completing and submitting IRS Form SS-4. The form may be submitted to the IRS by fax or by mail. (Note that although U.S. businesses may apply online for an EIN, this option is not available to foreign businesses.) The IRS will usually respond with the EIN within several days.