If a motion to transfer venue is not timely filed, the issue of improper venue is waived.
If a timely motion to transfer venue is filed, the venue issue is not waived by any other action in the case.
The reply shall set forth the basis for venue in the forum or state reasons why venue is not proper in one or more counties specified by the movant. The court shall not consider any basis not stated in the reply, nor shall the court consider allegations relating to fictitious defendants. If a reply is filed, the court may allow discovery on the issue of venue and shall determine the issue.
Mo. R. Civ. P. 51.045