Section 7486 - Time limitation on notices of deficiency and assessment of penalty and interest(a) The Commissioner may notify a taxpayer of a deficiency with respect to the payment of any tax liability, or assess a penalty or interest with respect thereto, in accordance with sections 3202 and 3203 of this title, at any time within three years after the date that tax liability was originally required to be paid under this chapter.(b) Notwithstanding subsection (a) of this section:(1) if the taxpayer fails to file a proper return with respect to any tax liability at the time prescribed for its filing, the notification or assessment may be made at any time before the end of three years after the taxpayer files such a return;(2) if the deficiency is caused by reason of fraud or the willful intent of the taxpayer to defeat or evade this chapter, the notification or assessment may be made at any time;(3) if the notice of deficiency or assessment is founded upon an assertion or determination by the United States that the taxable gifts or estate, or estate or gift tax liability of the taxpayer under the laws of the United States, is greater than such amount reported on any return of the taxpayer filed under the laws of the United States, the notification or assessment under sections 3202 and 3203 of this title may be made within the time prescribed under subsection (a) of this section, or at any time before the expiration of six months after the date the Commissioner is notified, in writing, by the taxpayer or by the United States of the federal assertion or determination, whichever period is the later to expire;(4) if the taxpayer and the Commissioner agree, the notification or assessment may be made at any time before the date so agreed upon; and(5) the running of the period of limitations for assessment or collection of any estate tax imposed by this chapter shall be suspended in respect of the estate of a decedent claiming a deduction under 26 U.S.C. § 2055(b)(2) as amended until 30 days after the expiration of the period for assessment or collection of the tax imposed by this chapter on the estate of the surviving spouse.Added 1969, No. 269 (Adj. Sess.), § 1, eff. date, see note under § 7401 of this title; amended 2017, No. 113 (Adj. Sess.), § 190.