Vote at Home Act of 2021 This bill expands voting by mail in federal elections and provides for automatic voter registration through state motor vehicle authorities. Specifically, the bill prohibits states from imposing additional conditions or requirements on the eligibility of individuals to cast ballots by mail in federal elections, except states may impose a deadline for returning a ballot. Further, states must mail ballots to individuals registered to vote in a federal election not later than two weeks before the election. In addition, the U.S. Postal Service must carry ballots for federal elections expeditiously and free of postage. Finally, the bill provides for automatic voter registration of individuals through state motor vehicle authorities.