When they issue a IP PIN in January of 2022 you are to use it for any/all returns you file during 2022 no matter which tax years they are for. So if you file the 2020 return back in 2021 you will not use the 2022 IP PIN on an already filed return. Read that notice again carefully to see exactly what/when you need to use it. Next year, in Jan 2023, they will mail you a new IP PIN to use for any/all returns you file in 2023.
