That is good to know, thank you. I found this helpful Q&A post and tried to follow the instruction, make a copy of the return and update the original return for which the credit was paid for, to file the 2nd Form 1120X.
But I could not make the "E-File Amendment" option clickable. It looks like I have to work on the copy and pay for another credit to file an amended return? Will the system allow me to use the copy to file an amended return without filing the original return first? This is my last chance to e-File so just want to make things right before acting... Much appreciated!