@nancyb1209 

You are referring to a recent [2022] IRS notification of late filing penalty on the 2020 1120S that you e-filed in 2021, right?   

Maybe an extension was e-filed on 3/15/21 and the final return was e-filed 12/31/21?  Was IRS e-file open for business entity e-file on 12/31/21?