(a)(1) In case of failure to pay:

(A) The amount shown as tax on a return on or before the date prescribed for payment of the tax, such date to be determined with regard to any extension of time for payment, there shall be added to the amount of tax required to be shown on the return one-half of 1 percent of the amount of the tax if the failure is for not more than one month and with an additional one-half of 1 percent for each additional month or fraction of a month during which the failure continues. For the purposes of this subparagraph, the amount of tax shown on the return shall be reduced, for the purpose of computing the addition for any month, by the amount of any part of the tax which is paid on or before the beginning of the month and by the amount of any credit against the tax which is claimed on the return;

(B) Any amount in respect of any tax required to be shown on a return which is not so shown within ten days of the date of the notice and demand for the payment, the amount of tax stated in the notice and demand shall be increased by one-half of 1 percent of the amount of the tax if the failure is for not more than one month and by an additional one-half of 1 percent for each additional month or fraction of a month during which the failure continues. For the purposes of this subparagraph, the amount of tax stated in the notice and demand shall be reduced, for the purpose of computing the addition for any month, by the amount of any part of the tax which is paid before the beginning of the month.

(2) No penalty shall be assessed pursuant to this subsection which exceeds in the aggregate 25 percent of the amount of the tax or when it is shown that the failure is due to reasonable cause and not due to willful neglect.

(b) With respect to any return, the maximum amount of the addition permitted under subparagraph (a)(1)(B) of this Code section shall be reduced by the amount of the addition under subsection (a) of Code Section 48-7-57 which is attributable to the tax for which the notice and demand are made and which is not paid within ten days of such notice and demand.

(c) If the amount required to be shown as tax on a return is less than the amount shown as tax on the return, subparagraph (a)(1)(A) of this Code section shall be applied by substituting the lower amount.

(d) For purposes of subsections (e) and (f) of this Code section, the term "underpayment" means a deficiency as defined in Code Section 48-7-1.

(e) If any part of any underpayment of tax required to be shown on a return is due to a negligent or intentional disregard of rules and regulations, but without intent to defraud, an amount equal to 5 percent of the underpayment shall be added to the tax.

(f) If any part of any underpayment of tax required to be shown on a return is due to fraud, an amount equal to 50 percent of the underpayment shall be added to the tax. This amount shall be in lieu of any amount determined under subsection (e) of this Code section. If any penalty is assessed under this subsection for an underpayment of tax which is required to be shown on a return, no penalty under Code Section 48-7-57 or subsection (a) of this Code section shall be assessed with respect to the same underpayment.

(g)(1) Notwithstanding any other provision of this Code section to the contrary, if:

(A) A joint return has been made for a taxable year;

(B) On such return there is an understatement of tax attributable to erroneous items of one individual filing the joint return;

(C) The other individual filing the joint return establishes that in signing the return he or she did not know, and had no reason to know, that there was such understatement;

(D) Taking into account all the facts and circumstances, it is inequitable to hold the other individual liable for the deficiency in tax for such taxable year attributable to such understatement; and

(E) The other individual has made the proper election pursuant to Section 6015 of the Internal Revenue Code, if applicable

then the other individual shall be relieved of liability for tax, including interest, penalties, and other amounts, for such taxable year to the extent such liability is attributable to such understatement, if such other individual has been relieved of liability for federal income taxes pursuant to Section 6015 of the Internal Revenue Code, if applicable.

(2) The commissioner shall promulgate any rules and regulations necessary to implement and administer this subsection.