Section 536 - Accuracy-related penalty(a) If this section applies to any portion of an underpayment of any tax imposed by this title or Title 4 required to be shown on a return, there shall be added to the tax an amount equal to 20% (40% in the case of gross valuation misstatements) of the portion of the underpayment to which this section applies.(b) This section shall apply to the portion of any underpayment which is attributable to 1 or more of the following: (1) Negligence or disregard of rules and regulations.(2) Any substantial understatement of tax.(3) Any substantial valuation misstatement with regard to any tax imposed by Chapter 11 or Chapter 19 of this title.(4) Any substantial estate or gift tax valuation understatement with respect to any tax imposed by Chapter 15 of this title.(c) For purposes of subsection (b) of this section, the following terms shall have the meanings ascribed to such terms in § 6662 of the Internal Revenue Code ( 26 U.S.C. § 6662 ), or successor provisions, except that "$1,500" shall be substituted for "$5,000" and "$3,000" shall be substituted for "$10,000" each place such dollar amounts appear in the said § 6662: (3) "Substantial understatement of income tax";(4) "Substantial valuation misstatement";(5) "Substantial estate or gift tax valuation understatement"; and(6) "Gross valuation misstatement."(d) For purposes of determining under subsection (b) of this section whether a portion of any underpayment is attributable to 1 or more of the items specified in paragraphs (b)(1)-(4) of this section, the provisions of § 6662 of the Internal Revenue Code ( 26 U.S.C. § 6662 ), or successor provisions, shall be applied in the same manner as if such provisions were applicable to the taxes imposed by this title or Title 4.(e) For purposes of this section, "underpayment" shall have the meaning ascribed to such term in § 6664(a) of the Internal Revenue Code ( 26 U.S.C. § 6664(a) ), or successor provisions. The penalty prescribed by this section shall apply only in cases where a return of tax is filed.68 Del. Laws, c. 187, §1; 71 Del. Laws, c. 353, § 15; 71 Del. Laws, c. 385, § 9.;