Mo. Rev. Stat. § 301.310: Owner may be instructed to replace plate — cancellation of registration — waiver of cost — penalty.

1. Whenever a law enforcement officer observes a plate to be in such condition as to hinder or make difficult identification of same, he shall notify the director of revenue and instruct the owner to apply for a duplicate plate.

2. If the owner has not made application within fifteen days, the director of revenue may cancel such registration and notify the registrant and such cancellation shall remain in force until the application has been filed.

3. The director of revenue may at his discretion replace worn plates without cost to the registrant.

4. Failure to surrender a mutilated or worn plate for which duplicate has been issued shall be* punishable under section 301.440.