Which type of PIN are you referring to? The 5 digit self-selected PIN for e-filing a tax return can be any 5 digit number. However, the 2018 AGI must be entered on the 2019 return and the 2019 AGI must be entered on the 2020 tax return.
If you are referring the 6 digit Identity Protection PIN that you received from the IRS each year due to reporting Identity Theft to the IRS, that IP PIN must be entered on each tax return whether e-filing or mailing.
