(a) Years other than years affected by a net operating loss carryback. If the taxpayer files a timely statement in accordance with the provisions of §1.9000-3, the amount of the increase in tax shown on such statement for a taxable year shall, except as provided in paragraph (b) of this section, be considered for all purposes of the Code, as tax shown on the return for such year. In general, such increase shall be assessed and collected in the same manner as if it had been tax shown on the return as originally filed. The provisions of this paragraph may be illustrated by the following example:

(b) Years affected by a net operating loss carryback. In the case of a year which is affected by a net operating loss carryback from a year to which an election under section 452 or 462 applies, that portion of the amount of increase in tax shown on the statement for the year to which the loss is carried back which is attributable to a decrease in such net operating loss shall not be treated as tax shown on the return.