"Under the tenant-based housing choice voucher program, the PHA issues an eligible family a voucher and the family selects a unit of its choice. If the family moves out of the unit, the contract with the owner ends and the family can move with continued assistance to another unit.
Under the project-based voucher program, a PHA enters into an assistance contract with the owner for specified units and for a specified term. The PHA refers families from its waiting list to the project owner to fill vacancies. Because the assistance is tied to the unit, a family who moves from the project-based unit does not have any right to continued housing assistance. However, they may be eligible for a tenant based voucher when one becomes available"