(a) Extension of period for assessment and refund or credit. Under section 5(e) of the Act, if an election is made to have the Act apply, and if the assessment of any deficiency, or the refund or credit of any overpayment attributable to the election, for any taxable year to which the Act applies was not prevented on June 21, 1959, by the operation of any law or rule of law (except as provided in paragraph (b) of this section, relating to closing agreements and compromises), but would be so prevented prior to September 1, 1961, the period within which such assessment, or such refund or credit, may be made with respect to such taxable year shall not expire prior to September 1, 1961. An election under either section 3 or 4 of the Act will be considered to be a consent to the extension of the period of limitation for purposes of assessment for any year to which the Act applies. Thus, for example, if, as the result of an election under section 4(a) of the Act, assessment of a deficiency for the taxable year 1955 was not prevented by the statute of limitations, a judicial decision that had become final, or otherwise, on June 21, 1959, but would (except for section 5(e) of the Act) be prevented on a later date, as for instance September 1, 1959, then for purposes of applying section 4 of the Act, assessment may be made at any time prior to September 1, 1961, with respect to such year if the taxpayer made an election under the Act prior to September 1, 1960. Section 5(e) of the Act will, in no event, operate to shorten the period of limitation otherwise applicable with respect to any taxable year.

(b) Years closed by closing agreement or compromise. For purposes of the Act, if the assessment of any deficiency or a refund or credit of any overpayment for any taxable year was not prevented on June 21, 1959, but is prevented on the date of an election under section 3 or 4 of the Act by the operation of the provisions of chapter 74 of the Code (relating to closing agreements and compromises), assessment, refund, or credit will, nevertheless, be considered as being prevented on June 21, 1959.