"Accident, mistake, or misfortune" means something outside the party's own control and not due to neglect, or something that a reasonably prudent person would not be expected to guard against or provide for.
N.H. Admin. Code § Tax 102.02
#2256, eff 1-2-83; ss by #2943, eff 12-31-84; EXPIRED: 12-31-90
New. #5638, eff 9-1-93; ss by #7068, INTERIM, eff 8-15-99, EXPIRES, 12-13-99; ss and moved by #7152, eff 12-10-99 (from Tax 101.02 ); ss by #8985, eff 9-24-07