Relating to the calculation of certain ad valorem tax rates of a taxing unit and the manner in which a proposed ad valorem tax rate that exceeds the voter-approval tax rate is approved; making conforming changes.

HB 139 updates how Texas local taxing units (like cities, counties, and school districts) calculate two key property tax rates when seeking to raise taxes beyond previous voter-approved limits. It modifies formulas for the "no-new-revenue tax rate" (which maintains current revenue levels) and the "voter-approval tax rate" (the threshold requiring voter approval for increases), adding specific multipliers (1.08 for special units, 1.035 for others) and accounting for revenue from new sales taxes. The bill directly affects local governments that collect property taxes, clarifying how they must compute these rates when adjusting tax levies. This is a technical adjustment to tax calculation procedures, not a new policy change.