South Carolina Rules of Civil Procedure
AMENDED AND SUPPLEMENTAL PLEADINGS
(a) Amendments. A party may amend his pleading once as a matter of course at any time before or within 30 days after a responsive pleading is served or, if the pleading is one to which no responsive pleading is required and the action has not been placed upon the trial roster, he may so amend it at any time within 30 days after it is served.
Otherwise a party may amend his pleading only by leave of court or by written consent of the adverse party; and leave shall be freely given
when justice so requires and does not prejudice any other party...