At the county BOE hearing, if the property is NOT a "qualified real property", the taxpayer carries the burden of proof, unless the County Assessor asserts a greater fair market value than the original assessed value. In that instance, the County Assessor carries the burden of proof, and the original assessed value will lose the presumption of correctness. If both parties argue against the original assessed value, both parties carry the burden of proof.
If the property IS a "qualified real property", the burden of proof lies with the County Assessor if they assert a fair market value equal to or greater than the inflation-adjusted value, which is presumed to equal fair market value. If the taxpayer asserts a lower fair market value than the inflation-adjusted value, the burden of proof lies with the taxpayer. If both parties argue against the inflation-adjusted value, both parties carry the burden of proof.