System verifiability or auditability is becoming an increasingly important feature for electronic voting systems. Electronic counting systems have a natural audit trail of the (often paper) ballot, so additional verifiability mechanisms are less important for such systems. With DRE voting machines, and also with remote electronic voting, there is no obvious way for the voter to be sure their ballot choices have been recorded or counted accurately. 

This lack of transparency was one of the main motivations for the development of the aforementioned VVPAT. Electronic voting machines with a VVPAT store the voter’s ballot choices electronically but also on a paper record, often within the voting machine. This allows the voter to check that their ballot choices have been recorded accurately on the paper record. Electronic results produced by the electronic voting machine can then be checked against paper records, verified by the voter, to ensure the electronic result reflects the voter’s choices.⁹

However, use of VVPAT solutions is not without complications, especially with respect to the internal printer. Other schemes have been developed to provide the voter with some form of receipt so they can individually check that the vote has been received and counted accurately. This transparency has to be accomplished without violating the secrecy of the vote, which is a challenge. 

End-to-end verifiable systems provide mechanisms for any oversight body to check that votes are received as cast, recorded as received and counted as recorded (i.e., all stages of the process function correctly and accurately). The voter will have some role in this verifiability, as only they know how they intended to cast their vote. Some end-to-end voting schemes provide the voter with a code they can use to check, after Election Day, that their vote has been included in the count with the correct value. Other schemes limit the role of the voter to checking the vote was received and recorded accurately, and provide other independently-verifiable proof that recorded votes are counted accurately.

^{9 For more detailed information on verifiability, please refer to the following subsection in Part 2: Design Requirements.}