When I try to email a 1040-X, it failed and said the clients SSN was previously used to E-file a tax return before.

[Allen5]

I deleted the original tax return and still got the massage the SSN was used before.

[Just-Lisa-Now-]

Sounds like youre not marking for Amended EF correctly, it still thinks its an original.  And you really should be using the original file as the amended file....if you want to keep a copy of the wrong original, use Save As and give it a different name, but use that actual original file (with the original file name) and amend it.

https://proconnect.intuit.com/community/amend-tax-return/help/how-do-i-amend-an-individual-return-us...