Wyo. Stat. § 36-9-109
When any state land shall have been purchased according to law, the board shall make and deliver to the purchaser a certificate of purchase, which shall contain the name of the purchaser, a description of the land purchased, the sum paid, the sum remaining unpaid, the amount of annual payments, which shall include the accrued interest, upon the amortization plan as hereinbefore defined, and the date on which each of the deferred payments falls due. All annual payments shall be due and payable on the first day of December of each year, provided that interest is paid on the full amount of the deferred payments at the rate of four percent (4%) per annum from date of the sale to the first day of December following such date of sale.
W.S. 36-9-109