Wyo. Stat. § 16-4-302: Competent evidence of delivery.

If any report, claim, tax return, statement or other document or payment is sent by United States mail and either registered or certified, a record authenticated by the United States post office of the registration or certification is competent evidence that the report, claim, tax return, statement or other document or payment was delivered to the state officer or state agency or officer or agency of the political subdivision to which addressed, and the date of registration or certification is deemed the postmarked date.