Utah Code § 17-3-9
Whenever a new county shall be created under the provisions of this chapter and the officers thereof shall have duly qualified the county treasurer of the county from which territory has been taken to create such new county shall furnish to the county treasurer of such new county a certified list of all taxes collected by the county treasurer of the county from which territory has been taken for the preceding year upon the property located within such portion of that county as has become a part of such new county, together with the entire amount of such county, district school or other special taxes collected by the county treasurer of the county from which territory has been taken for such preceding year, less the pro rata cost of assessing and collecting the same and the entire cost of making said certified lists.
Utah Code § 17-3-9