Mo. Rev. Stat. § 329.120

The holder of a license issued by the board who continues in active practice or occupation shall on or before the license renewal date renew the holder's license and pay the renewal fee. A license which has not been renewed prior to the renewal date shall expire on the renewal date. The holder of an expired license may have the license restored within two years of the date of expiration without examination, upon the payment of a delinquent fee in addition to the renewal fee.