Sometimes, it's hard to create an incorrect return. I go for easy. If the original return is not in my software:
Create the return as it should be, as if it's the original return and not an amendment.
When I have the return the way it should be, I call up the X forms (I've done this at Block, with ATX, and with ProSystem fx, but ATX was a long time ago).
When your software asks you if you want to transfer the data to "Column C," say NO or check/uncheck the box or however your software works to keep your data as amended now.
Then you just have to type into "Column A" the amounts from the client's original return and add the explanation.
This is often a whole lot easier than trying to recreate your client's original return in your software, especially if he had errors. And, it's easier for me to proofread the return I'm creating as if it's an original return, then turn it into an amendment. I can follow the flow better.