Mo. Rev. Stat. § 32.058

32.058. First class mail permitted to send documents, when — electronic delivery of documents permitted, when — burden of proof — definitions. — 1. Notwithstanding any provision of law requiring the use of certified mail or registered mail to the contrary, including but not limited to provisions contained in chapters 32 , 105 , 135 , 140 , 142 , 143 , 144 , 148 , 149 , 238 , 253 , 301 , 302 , and 479 , the director may choose to mail any document by first class mail to the intended recipient's last known address in lieu of certified mail or registered mail. If the director is otherwise statutorily required to use certified or registered mail to send a document, but chooses pursuant to this section to send such document by first class mail, and the director is subsequently notified by the United States Postal Service that the document is not deliverable to the intended recipient at the last known address for a reason other than refusal by the addressee, the director shall make one further attempt to reissue such document after attempting, if necessary, to obtain an updated mailing address. Nothing in this section prohibits the director from making multiple additional attempts to reissue the document.

2. The delivery of a document using email, encrypted electronic message, or both, including by an attachment to such email or encrypted electronic message, shall satisfy any obligation of the director to send such document to the intended recipient by certified mail, registered mail, or any other method.

3. Notwithstanding any other provision of law to the contrary, in any action before the administrative hearing commission or a court of competent jurisdiction, the director shall bear the burden of proving the date any document has been sent to the taxpayer's last known address, and the period of time within which a taxpayer may appeal or otherwise respond to any such document shall begin on the date the document is sent. This provision shall not apply if the taxpayer fails to update the department with a new address within thirty days of any change of address.

4. As used in this section, the following terms mean:

(1) "Director" , includes the director of revenue, the department of revenue, and any division thereof; and

(2) "Document" , includes, but is not limited to, any notice, request, record, assessment, decision, order, letter ruling, agreement, or certificate, whether in electronic or nonelectronic form.

(L. 2026 H.B. 2180)