Hello Lisa 

I am going to file an amended return 2021 1040X which original return 1040 had efiled by other tax preparer 

I follow the instruction when the professional proseries software popped up amended instruction for 1040X. I prepared original as other tax preparer did and saved as another file . It caused more problem (duplicate ssn and duplicate file):( Sad.

Now I read your link , line 3. It looked like I cannot file amended return 1040 if original return did not go through proseries . It is correct ???

Copy from your link posted

"3.Can all Individual Amended filing types be e-filed?
Only an e-filed Form 1040 can be amended. An original return that was paper filed cannot have an e-filed amended return. The original return must have been e-file through your ProSeries software."