In determining whether payment of a tax is timely received, if it is known that the postal service was inoperative at a certain time due to strikes, riots, warfare, acts of God or other reasons, the Department will consider the circumstances, and if there is any evidence of timely mailing, the Department will accept that evidence and consider the mailing to have been made timely.
Nev. Admin. Code § 366.102
NRS 366.110, 366.370