Under state law and Ohio Department of Taxation rules, real property in all counties is reappraised at 100 percent of market value every six years (Revaluation) and updated the third year (Triennial Update) after each reappraisal. Thirty-five percent of the market value represents the assessed or taxable valuation of real property.

In order to verify that real property is being assessed at or close to 35 percent of market value, the Department of Taxation surveys real property transferred. Sales ratios are calculated by dividing the total assessed (taxable) value of the transferred properties by the total consideration (sales price) paid for those properties.