In Germany you get a letter with an invitation to vote automatically for every election. This is based on the general resident registry, and you're required to

In Germany you get a letter with an invitation to vote automatically for every election. This is based on the general resident registry, and you're required to register when you move. To vote you simply have to bring that letter with you, and then you usually don't need to show any ID. The election officers can still ask you for it if there is any doubt about your identity. Just before you enter your ballot your name is checked against the voter registry and crossed out from it. Of course that still leaves a bit of fraud potential, but not really on any scale that would affect the election. You'd still need to forge the letter and know the personal details of a voter that won't vote themselves.