The IRS no longer uses electronic filing personal identification numbers (PINs). Instead, you will enter your Adjusted Gross Income (AGI) from last year’s tax return. Learn more about using your AGI to verify your identity here.
If you self-selected your PIN last year, you can use it to file as well. This would be a five digit number, except for all zeroes, that you selected when filing your taxes last year. For more information, check out the IRS website.