Because of the wide range of responsibilities performed by the assessor-collector, most citizens deal with this county official more frequently than any other office.

The major tax duty of the assessor-collector, who collects property taxes, is the assessment (calculation) of taxes on each property in the county and collection of that tax as established by the Constitution and the State Property Tax Code. In addition, as an agent of the Texas Department of Transportation, the assessor-collector is responsible for the registration and licensing of motor vehicles owned by residents of the county.

Another duty of the county tax assessor-collector is that of voter registrar. In most Texas counties, a person would register to vote through the office of county tax assessor-collector. In a few counties, the commissioners court has designated the county clerk or an elections administrator to provide this function. The county tax office voter registration responsibilities include accepting applications for voter registration, issuing voter certificates, maintaining voter registration lists, verifying petitions for local option elections and submitting required reports to the Secretary of State's Office.

The county tax assessor-collector is also responsible for the collections of special fees imposed by the county and state on coin-operated vending machines, alcoholic beverage permits and registration and titling boats.