Texas has required some form of identification to vote at the polls since 2003. In the decade after, before the new law imposed even stricter requirements, some 20 million votes were cast, Solicitor General Donald B. Verrilli Jr. told the justices, while “only two cases of in-person voter-impersonation fraud were prosecuted to conviction."
But I'm sure you can conclude that these 18 confirmed cases represent the total.