Wyo. Stat. § 15-6-432
If any city or town issues bonds to pay the cost and expense of any local improvement, the cost and expense shall be assessed against the lots, tracts and parcels of land and other property liable. The ordinance levying the assessment shall provide that the sum charged against each may be paid during the thirty (30) day period as provided in W.S. 15-6-439, unless the legal owners of record of all property assessed in the district waive that thirty (30) day period. The ordinance levying the assessment shall specify whether the sum remaining unpaid is payable in equal annual or semiannual installments for a period of years equal to that which the bonds issued to pay for the improvement run, with interest upon the whole unpaid sum at a rate fixed by ordinance, or in equal level annual or semiannual installments of principal and interest thereon at a rate fixed by ordinance for a period of years equal to that period for which the bonds to pay for the improvements were issued.
W.S. 15-6-432