An S corporation (Form 1120-S) must file its return by:
- The 15th day of the third month after the tax year-end (March 15 for calendar-year S corporations), with a 6-month automatic extension available. (correct answer)
- April 15, the same as individual returns.
- The 15th day of the fourth month after the tax year-end.
- The same due date as the C corporation return (Form 1120).
Explanation: S corporations file on the same schedule as partnerships - 15th day of the third month (March 15 for calendar year), with a 6-month extension. Answer A is correct. April 15 (B) is for individuals. Fourth month (C) is for C corporations. S corps have an earlier due date than C corps (D).