Shouldn't be getting a duplicate if that was the case.
Is this for an individual return?
Could the client have used the non filer site to get the stimulus?

Oh wait, you say "second file"...you should use the same file for the return that you used for the extension.

Not an individual return.  I filed the 1065 extension.  Not sure why getting error message.  I have the complete partnership file ready to efile but it won't allow says duplicate SSN/EIN.

I tried to delete the first file - no can do.

I tried to edit the EIN on the first file so not a duplicate - no can do.

Any suggestions?  Other than re-entering ALL that data .. on a time crunch.

understood - is there a work around short of rekeying everything into the first file?  Did not intend a 2nd file -not sure why it generated.

Not sure why you created a second file for the return rather than using the same one you used for the extension....now the program thinks its 2 different company returns with the same EIN.

Either re-enter all the data into the correct file and Efile it....or print and mail the return are going to be your only options.

If its a partnership return youre not on a time crunch, the extension gives you until September to file