Why is state tax so high just moved into South Carolina in December

Be sure you are filing part year resident returns for both of the states where you lived in 2020.  But did you work in SC or have other SC-based income prior to your move?

You may not have allocated the correct amount of your income to South Carolina.  In your South Carolina return, at the very beginning, there is a page where you select whether to file as:

• Resident OR part-year resident filing as a resident
• Nonresident OR part-year resident filing as a nonresident

Select "Nonresident OR part-year..."

 

Further in the program, there is a page where you allocate to South Carolina, the income earned while you were living or working there.  See screenshot below.