i think the easiest way to do it, would be create a digital ballot tied to your TaxID. Requires much more information to pay taxes than it does to vote. and the IRS. Even people who are exempt from taxes still have to file.

Once you file taxes a new ballot key is issued/tied to your identity. Can literally scan your state id barcode. Ballot printed on the spot, and ballot key is destroyed.

Polling station immediately closes down once the ballot limit is reached.

The state and federal will know exactly the eligible amount of voters down to the county. Keep a running tally all year online.

Impossible to have extra ballots floating around. The dead don't file taxes. If you don't file taxes...I guess you are not voting.