Subject to subsection (b) of this section, the governing body of Garrett County may reduce, by law, the percent of the assessment on one or more classes or subclasses of personal property listed under § 8-101 of this article. If Garrett County reduces or eliminates the percentage of assessment of taxable personal property under subsection (a) of this section, Garrett County shall submit a copy of the law to the Department. If the Department receives a copy of the law on or before March 1, the change shall be effective for the taxable year following the date the law is enacted.