Contact the Internal Revenue Service (IRS) on their national call centre number and follow the prompts to speak to an agent in the Business Tax Department. The IRS agent will need your business name and possibly your Social Security number. Once your business has been verified and located in the system they will mail the certificate to the address you initially used to register your business. For security purposes, they may not mail a copy of the certificate to any other address.
Ask the IRS agent to fax a copy of the certificate to your fax machine. Having your EIN certificate faxed will not be the original letter you received when you first obtained your tax ID number but it will be a letter on IRS letterhead informing your business of the request being made for a copy of your EIN number.
You could try speaking with your tax accountant or registered agent to see if he has a copy of your EIN certificate. If you hired an accountant to file your taxes he may have the original copy of your EIN certificate. Accountants would need to access this information regularly when they process your state and federal taxes. Your registered agent, who possibly incorporated your business, may also have this information if you allowed him to register for your EIN is well. Contact both to see if they can send you a copy.