26 C.F.R. § 1.9005-3
Notwithstanding any provision of law to the contrary, the period within which the assessment of any deficiency attributable to the election may be made, or within which the credit or refund of any overpayment attributable to the election may be made, shall not expire sooner than one year after the last day for making the election. Thus, if assessment of a deficiency or credit or refund of an overpayment, whichever is applicable, was not prevented on September 26, 1961, the time for making assessment or credit or refund shall not expire for at least one year after the last day for making the election. Even though assessment of a deficiency was prevented on September 26, 1961, if commencement of a suit for recovery of a refund under section 7405 of the Internal Revenue Code of 1954 may have been made on such date, then any deficiency resulting from the election may be assessed at any time within one year after the last day for making the election. If a taxpayer makes the election, he shall be deemed to have consented to the application of the provisions of section 2 of the Act extending the time for assessing a deficiency attributable to the election. Section 2 of the Act does not shorten the period of limitations otherwise applicable. An agreement may be entered into under section 6501(c)(4) of the Internal Revenue Code of 1954 and corresponding provisions of prior law to extend the period for assessment.
26 C.F.R. §1.9005-3
Sec. 2(f), 75 Stat. 683; 26 U.S.C. 613 note