For those people who are re-registering due to address change, there is no 30-day requirement. They are allowed to vote even if they are within the 30 day period.
College students may register to vote either in the county in which they live while attending college or at their previous address, but not both.
You must register using a street address (not a P.O. box). College students whose mailing address includes a P.O. box should include the name of their dorm as well.
If you have moved since previously registering, even on the same street, you must register again with your new address. In short, the address on your photo ID must match the address on your voter...
People who have been convicted of felonies ARE ELIGIBLE to vote in South Carolina AFTER they have completely served their sentences, including probation or parole.