Section 622.105 - Evidence of date mailed1. Any report, claim, tax return, statement, or any payment required or authorized to be filed or made to the state, or any political subdivision which is transmitted through the United States mail or mailed but not received by the state or political subdivision or received and the cancellation mark is illegible, erroneous or omitted, shall be deemed filed or made and received on the date it was mailed if the sender establishes by competent evidence that the report, claim, tax return, statement, or payment was deposited in the United States mail on or before the date for filing or paying. In the event of nonreceipt of any such report, tax return, statement, or payment, the sender shall file a duplicate within thirty days of receiving written notification of nonreceipt of such report, tax return, statement, or payment. Filing of a duplicate within thirty days of receiving written notification shall be considered to be a filing made on the date of the original filing.2. For the purposes of this section "competent evidence" means evidence, in addition to the testimony of the sender, sufficient or adequate to prove that the document was mailed on a specified date which evidence is credible and of such a nature to reasonably support the determination that the letter was mailed on a specified date.