The office shall perform all duties relating to the assessment and collection of taxes on motor vehicles in the county and issue applications for certificates of title on vehicles, which have heretofore been performed by the tax collector, tax assessor, and the probate judge. The license commissioner shall receive the commissions and fees for performing these functions, and such fees and commissions shall be remitted to the county general fund. Reporting and remitting of the tax shall be made at the same time as other reports and remittances are now made.