South Carolina (SC) automatically gives you a 6-month extension to October 15 if you filed an approved federal extension and don't owe taxes to South Carolina. Otherwise, mail Form SC4868 by April 15. If you owe, submit payment by April 15 to avoid penalties. You can either include a check with Form SC4868 or submit an extension payment at their MyDORWAY site (if paying online, you don't need to send Form SC4868).