S.C. Code Ann. § 12-54-55: Interest on underpayment of declaration of estimated tax.

In the case of an underpayment of declaration of estimated tax by an individual, estate, trust, or corporate taxpayer, instead of all other penalties provided by law, there must be added to the tax for the taxable year a penalty to be determined as follows:

(1) in the case of an individual taxpayer, estate, or trust in the same manner as prescribed by the provisions of Internal Revenue Code Section 6654 and applicable regulations except that the small amount provisions are one hundred dollars. No interest or penalty is due under this item for underpayments attributable to personal service income earned in another state on which income tax due the other state was withheld;

(2) in the case of a corporate taxpayer, in the same manner as prescribed by the provisions of Internal Revenue Code Section 6655 and applicable regulations, except that the small amount provisions are one hundred dollars.