Raleigh, N.C. Oct 12, 2020 Taxpayers who received 6-month extensions on their state individual income tax returns in April must file those returns by Thursday, Oct. 15. Taxpayers who mail those returns to the N.C. Department of Revenue must have them postmarked by Oct. 15. E-filed returns must be sent electronically by midnight on Oct. 15. The April 15 deadline to file individual income tax returns was extended until July 15 this year. However, anyone who requested the automatic extension before the July 15 filing deadline must file by Oct. 15.