I hope that the outer “certification” return ballot envelope is also required to be retained.
I live overseas so the franking part of the ballot doesn't work for me. I have to put the entire ballot as it would have been mailed in the USA inside of a regular envelope then pay the postage from Spain to get it to my local election commission in Georgia. When they receive it they make an electronic note of it that I can look up online. For example, my ballot for this latest election was received on 17 October. But if there was a challenge somewhere down the line I wonder if they save the original envelope I sent it in for proof or if they end up with an official ballot that has no postmark?
In our state it is, because it contains the signature. Each ballot must have a corresponding name/signature whose name appears on the role of registered voters. . (One person: One vote SCOTUS Gore-Bush). Any without is null and void.