The deadline to file your South Carolina return is April 15th, 2026 unless you have a valid extension.
According to the South Carolina DOR:
"If you file using a calendar year end of December 31", your Estimated Tax payments are due in four equal installments:
- 1st quarter due April 15, 2026
- 2nd quarter due June 15, 2026
- 3rd quarter due September 15, 2026
- 4th quarter due January 15, 2027