Employer Identification Number (EIN) is a unique nine-digit number assigned by the IRS. The IRS uses the number to identify taxpayers who are required to file various business tax returns like 2290. EIN is also known as Federal Employer Identification Number (FEIN) or the Federal Tax Identification Number. One of the fastest ways to do so is by calling the IRS. The IRS has a specialty tax line where you can call 800-829-4933 and ask any questions you may have about finding or applying for an EIN. The line is open Monday through Friday from 7:00 am to 7:00 pm local time, so be sure to call during those hours. Contact the IRS at their Business and Specialty Tax Line: (800) 829-4933. Call between 7 a.m. and 7 p.m. local time, Monday through Friday. A representative will request some identifying information from you in order to look up your trust's EIN and confirm that you're authorized to receive it. If you don't have authority, the IRS will send the CQm0.