The SAVE America Act would require all Americans to present documentary proof of citizenship, such as a passport or birth certificate, when registering to vote in federal elections. Currently, Americans sign a form under penalty of perjury when registering to vote. The Help America Vote Act of 2002 allows driver's licenses and last four digits of a Social Security number for registration. Only 48% of Americans have a valid passport. After Kansas adopted a similar requirement in 2013, roughly 31,000 eligible citizens — 12% of applicants — were blocked from registering.