credit to which such assessment relates had been properly claimed. . (2) Application to CARES Act credit Section 2301 of the CARES Act is amended by adding at the end the following new subsection: (o) Extension of limitation on assessment (1) In general Notwithstanding section 6501 of the Internal Revenue Code of 1986, the limitation on the time period for the assessment of any amount attributable to a credit claimed under this section shall not expire before the date that is 6 years after the latest of— (A) the date on which the original return which includes the calendar quarter with respect to which such credit is determined is filed, (B) the date on which such return is treated as filed under section 6501(b)(2) of such Code, or (C) the date on which the claim for credit or refund with respect to such credit is made. (2) Deduction for wages taken into account in determining improperly claimed credit (A) In general Notwithstanding section 6511 of such Code, in the case of an assessment attributable to a credit claimed under this section, the limitation on the time period for credit or refund of any amount attributable to a deduction for improperly claimed ERTC wages shall not expire before the time period for such assessment expires under paragraph (1). (B) Improperly claimed ERTC wages For purposes of this paragraph, the term improperly claimed ERTC wages means, with respect to an assessment attributable to a credit claimed under this section, the wages with respect to which a deduction would not have been allowed if the portion of the credit to which such assessment relates had been properly claimed. . (j) Effective dates (1) In general Except as otherwise provided in this subsection, the provisions of this section shall apply to aid, assistance, and advice provided after March 12, 2020. (2) Due diligence requirements Subsections (b) and (c) shall apply to aid, assistance, and advice provided after the date of the enactment of this Act. (3) Limitation on credit and refund of COVID-related employee retention