(a) Except as otherwise provided in this section, a notice of proposed assessment under § 521(c) of this title shall be mailed to the taxpayer within 3 years after the return was filed (whether or not such return was filed on or after the date prescribed). No deficiency shall be assessed or collected with respect to the taxable period for which a return was filed unless such notice is mailed within such 3-year period, or within the period otherwise prescribed in this section.

(b) In the case of a deficiency in any license fee or tax under Part III of this title, a notice of proposed assessment under § 521(c) of this title shall be mailed to the taxpayer within 3 years after the expiration date of the license to which the proposed assessment relates.

(c) If no return is filed, or if a false and fraudulent return is filed with intent to evade any tax imposed by this title or Title 4, a notice of proposed assessment under § 521(c) of this title may be mailed to the taxpayer at any time.

(d) If the taxpayer fails to comply with the requirement of § 514 of this title by not reporting a change or correction to the federal income or estate tax return, or by not filing an amended return under this title, a notice of proposed assessment under § 521(c) of this title may be mailed to the taxpayer at any time.

(e) If the taxpayer shall, pursuant to § 514 of this title, report a change or correction or file an amended federal income or estate tax return increasing the federal tax liability, a notice of proposed assessment under § 521(c) of this title with respect to such change or correction (if not otherwise deemed to have been assessed under § 530(a) of this title upon the filing of such report or amended return) may be mailed to the taxpayer at any time within 2 years after such report or amended return was filed.

(f) Where, before the expiration of the time prescribed in this section for the mailing of a notice of proposed assessment under § 521(c) of this title, both the Director and the taxpayer shall have consented in writing to such assessment after such time, the proposed assessment may be assessed at any time prior to the expiration of the period agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon. An agreement between the taxpayer and the Internal Revenue Service providing for the extension of the period for assessment of federal income taxes shall constitute an agreement with the Director to extend the period for assessment of income taxes under this title. A copy of any such agreement between the taxpayer and the Internal Revenue Service shall be filed by the taxpayer with the Director within 30 days after its execution.

(g) For purposes of this section, a return filed before the last day prescribed by law or by regulation promulgated pursuant to law for the filing thereof shall be considered as filed on such last day.

(h) The running of the period of limitations provided for in this section on the making of assessments shall, in a case under Title 11 of the United States Code, be suspended for the period during which the Director is prohibited by reason of such case from making the assessment plus 60 days thereafter.

(i) If a taxpayer omits from a return any amount of income, gross gifts or gross estate properly includible therein which exceeds 25% of the amount stated on the return, the tax may be assessed at any time within 6 years after the return was filed. If a taxpayer omits from a return any amount of license fee or tax under Part III of this title includible therein which exceeds 25% of the amount stated on the return, the tax may be assessed at any time within 6 years after the expiration date of the license to which the proposed assessment relates.

68 Del. Laws, c. 187, § 1; 70 Del. Laws, c. 186, § 1; 71 Del. Laws, c. 144, § 1; 71 Del. Laws, c. 385, §§ 7, 8; 72 Del. Laws, c. 112, § 3; 81 Del. Laws, c. 19, § 1.