Ariz. Rev. Stat. § 28-8346 – Filing by mail; date of filing

A. On receipt of any notice, affidavit, application, registration or other document that must be filed with the department pursuant to this article after the date on which the document is required to be filed and received, the department shall treat the document as if it had been received on the required date if both:
1. 1. It is transmitted through the United States mail.
2. 2. The envelope in which the document is enclosed has a post office cancellation mark dated on or before the required date.
B. If the sender disputes the dates contained on the mark or if a mark does not appear or is not legible, the mailing date may be established by competent evidence introduced by the sender.