An LC diagnostic says that e-filing of the 1040X is only allowed when the original return was electronically filed. See Ref 55285.  What would be the consequence of e-filing the 1040X?  Since my client's return has a balance due I'm going to e-file unless there is a compelling reason not to do so.

P..S the RTRP who did the original return prepared it manually AND did not list round numbers.  WHO DOES THAT?!  Adding cents is adding an additional chance for arithmetic errors. Furthermore, I think that indicates a lack of professionalism and perhaps padding the time spent and padding the bill as a result.