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The IRS will not re-issue or provide a copy of the CP575 Letter.
If you lost your original letter and need to confirm your EIN - the IRS will send you the letter 147C that may be used when you are asked for the CP575 Letter.
Also - in lieu of the IRS Form CP575, the applicant may use any official correspondence, such as the quarterly tax payment coupon, from the IRS showing the name of the entity as shown on the application and the EIN.
You may send a written request for the letter 147C to the IRS - but that would be faster to call and request on the phone.
For copy you need contact IRS via the phone. Call 1-800-829-4933_ from 7:00 a.m. to 7:00 p.m. local time.
See also here - http://www.irs.gov/businesses/small/article/0,,id=155444,00.html
Let me know if any clarification needed.