Abbreviation of “identity protection personal identification number.” This is a six-digit number that prevents someone else from filing a tax return with your Social Security number (SSN) or individual taxpayer identification number (ITIN). The IP PIN is known only to you and the IRS. It helps the IRS to verify your identity when you file your electronic or paper tax return, and it helps to prevent tax-related identity theft and the stealing of tax refunds. Anyone with an SSN or an ITIN can get an IP PIN, including individuals living outside the US. See the IRS website’s information page about the IP PIN.