In order to e-file the amended tax return, the system needs to see the acknowledgement of the original return. It can only do that with the original tax return.

You have to stay in the original return to complete the amendment. If you choose 'save as' and give it a new name, when you open the new file, it does not recognize that it was originally filed.

To keep a copy of the original before amending, go to where you save your copies of the tax return and rename it there. Something such as adding "Original" to the name.

That way when you save the amendment it will not override it.