Mo. Rev. Stat. § 341.180
An applicant for a master plumber's license or a master drainlayer's license shall deposit with the application a fee in the sum of ten dollars; and an applicant for a journeyman plumber's license or a journeyman drainlayer's license shall deposit with the application a fee in the sum of two dollars. The term of all licenses shall be one year and such license may be renewed by application therefor to the board of plumbing and sewer inspection upon the payment of the license fee herein provided. The failure to secure a renewal license on or before the expiration of the original license shall require the applicant for such license to submit to reexamination upon the same terms and conditions imposed upon new applicants. The license fee deposited with the applicant's application shall be forthwith paid into the county treasury. Any applicant failing to pass a satisfactory examination for a license may submit a new application for examination, ninety days after the date of the original application, accompanied by the examination fee provided herein.
§ 341.180, RSMo