Mo. Rev. Stat. § 346.080
If a hearing instrument specialist in-training under this section or section 346.075 has not successfully passed the licensing examination within one year from the date of issuance of the temporary permit, the temporary permit may be renewed by the division once for a period of six months upon payment by the applicant of a fee, as defined by division rule.
(L. 1973 H.B. 396 & 257 § 16, A.L. 1981 S.B. 16, A.L. 1995 S.B. 69, et al.)