Replacing a Lost IP PIN
Lost IP PINs
Taxpayer IP PIN holders who have lost or misplaced their numbers are to contact the IRS.
Should you receive a CP01A Notice that contains your IP PIN, yet that of which has been lost or misplaced, you may call us for specialized assistance at 1-800-908-4490, Monday - Friday, 7 a.m. - 7 p.m. your local time (Alaska and Hawaii are Pacific Standard Time).
You must verify your identity to the assistant. Your IP PIN will then afterwards be issued to you at your address of record.
Links from the IRS.gov website