Section 47-4301 - Periods of limitation(a) Unless otherwise provided in subsection (d) of this section, the amount of a tax imposed under this title shall be assessed within 3 years after the return was filed (whether or not the return was filed after the date due) or, if the tax is payable by stamp, at any time after the tax became due and before the expiration of 3 years after the date on which a part of the tax was paid. A proceeding in court without assessment for the collection of the tax shall not commence after the expiration of such period. For purposes of this chapter, the term "return" means the return of tax required to be filed by the taxpayer (and does not include a return of tax of a person from whom the taxpayer has received an item of income, gain, loss, deduction, or credit).(b) For purposes of this section, a return filed before the last day prescribed by this title, or by regulations promulgated under this title for filing, shall be considered as filed on the last day.(c) The execution of a return by the Mayor shall not start the running of the period of limitations on assessment and collection.(d)(1) In the case of a (A) false or fraudulent return with the intent to evade tax, (B) willful attempt in any manner to defeat or evade tax imposed by this title, (C) failure to file a return, or (D) filing a real property tax exemption application, the tax may be assessed, or a proceeding in court for the collection of the tax may begin without assessment, at any time.(2)(A) In the case of a tax imposed by Chapter 18 of this title, if the taxpayer omits an amount properly includible in gross income which is in excess of 25% of the amount of gross income stated in the return, the tax may be assessed, or a proceeding in court for the collection of the tax may be begun without assessment, at any time within 6 years after the return was filed. In the case of a trade or business, the term "gross income" means the amount received or accrued from the sale of goods or services (if the amounts are required to be shown on the return) before diminution by the cost of the sales or services.(B)(i) For the purposes of subparagraph (A) of this paragraph, an understatement of gross income by reason of an overstatement of unrecovered cost or other basis is an omission from gross income.(ii) This subparagraph shall apply to returns filed:(I) After [February 18, 2017]; and(II) On or before [February 18, 2017] if the applicable assessment period provided for in this section for assessment of the taxes with respect to the return has not expired as of the date return was filed.(3) In the case of a return not under Chapter 18 of this title, if the taxpayer omits from the return an amount of tax properly includible on the return which exceeds 25% of the amount of the tax reported on the return, the tax may be assessed, or a proceeding in court for the collection of the tax may be begun without assessment, at any time within 6 years after the return is filed.(e) If, before the expiration of the time prescribed in this section for the assessment of a tax imposed by this title, both the Mayor and the taxpayer have consented in writing to its assessment after such time, the tax may be assessed at any time before the expiration of the extended period. The period may be extended further by subsequent agreement in writing made before the expiration of an extended period.(f) If the amount of taxable income for a taxable year (or portion of a taxable year) of a taxpayer as reported by the taxpayer, or his duly authorized agent, to the United States Department of Treasury for federal income tax purposes is changed or corrected by the Commissioner of Internal Revenue, by a court of the United States, or by a court of the District of Columbia, or if the amount of taxable income for a taxable year (or portion of a taxable year) of a taxpayer as reported by the taxpayer or his duly authorized agent, to the District of Columbia for District of Columbia income or franchise tax purposes is changed or corrected by a court of the United States or the District of Columbia, the taxpayer, or his duly authorized agent, shall, within 90 days after the change or correction is finally determined, report in writing the changed or corrected taxable income to the District of Columbia. The Mayor may, within 180 days from the date of the receipt of written notice from the taxpayer of the changed or corrected taxable income as finally determined, assess or reassess the amount of a tax imposed by this title; provided, that if the date of receipt by the District of Columbia of a notice from the taxpayer is more than 180 days before the expiration of the applicable period of limitation, the Mayor shall have until the expiration of the applicable period of limitation to assess or reassess the amount of the tax. Failure to report the changed or corrected taxable income as finally determined within the 90-day period shall suspend the running of the period of limitation for a period of 180 days after the date that the report from the taxpayer, or his duly authorized agent, is received by the District of Columbia.June 9, 2001, D.C. Law 13-305, § 404(b), 48 DCR 334; Apr. 4, 2003, D.C. Law 14-282, § 11(bbb), 50 DCR 896; Feb. 18, 2017, D.C. Law 21-188, § 2, 63 DCR 14368.Section 410(b) of D.C. Law 13-305, as amended by section 36(b) of D.C. Law 14-213, provided: "Except as otherwise provided therein, sections 403 and 404 shall apply to taxes other than the real property tax imposed under Chapter 8 of Title 47, for all tax years or taxable periods beginning after December 31, 2000."