What specific forms need to be attached with a South Carolina tax return?

As far as 1099-series forms, South Carolina only requires that you attach 1099s that show South Carolina withholding.

For other forms or documents that may need to be attached to your South Carolina return, please see "BEFORE YOU FILE" on page 4 of 2018 SC 1040 INDIVIDUAL INCOME TAX FORM AND INSTRUCTIONS. 

If you're efiling through TurboTax, any required documents will be automatically attached to your efiled return.