The Preparer Tax Identification Number (PTIN) is an identification number that all paid tax return preparers must use on U.S. federal tax returns or claims for refund submitted to the Internal Revenue Service (IRS).

An EFIN—or Electronic Filing Identification Number—is a unique six-digit number issued by the IRS to individuals or organizations that are approved to electronically file tax returns. It’s essentially your official credential for participating in the IRS e-file program.