The unification charter form of government is similar to the metropolitan model; however, while the latter form is available to all counties, the unification form is available only to counties with a county or metropolitan charter. T.C.A. §§ 7-21-101 through 7-21-408.  The unification government charter process may differ somewhat from that of the metropolitan government charter process. The unification government charter commission may be initiated by proclamation of the county mayor or resolution of the county legislative body, but the mayor's proclamation is subject to ratification by the county legislative body. Also, the county's action must be approved by the legislative body of the most populous city in the county for a charter commission to be formed. A county proclamation must appoint eight members to the charter commission, then the city mayor appoints eight members, and one member is appointed by the mayor of any smaller city electing to participate. A noteworthy substantive difference from a metropolitan government is that the unification charter must provide for a chief executive and a legislative body of a limited size--nine to 19 members.

As of this writing no county has adopted a unification charter although it has been the subject of a vote in Knoxville and Knox County.