Federal returns and assessments, when copies are required

(a) In prescribing the form of return the department of taxation may require that a person who is required to file a federal income tax return include in the person's return a reconciliation of the return with the person's federal return, or that the person furnish with the return and as a part thereof a copy of the federal return. (b) It shall be the duty of every person who is required by section 235-92 to make a return, to report to the department, as to any taxable year governed by this chapter, if: (1) The amount of taxable income as returned to the United States is changed, corrected, or adjusted by an officer of the United States or other competent authority; (2) A change in taxable income results from a renegotiation of a contract with the United States or a subcontract thereunder; (3) A recomputation of the income tax imposed by the United States under the Internal Revenue Code results from any cause; or (4) An amended income tax return is made to the United States. The report shall be made within ninety days after the change, correction, adjustment, or recomputation is finally determined or the amended return is filed, as the case may be. The report required by this subsection shall be made in the form of an amendment of the person's return filed under this chapter. The amended return shall be accompanied by a copy of the document issued by the United States under paragraphs (1) to (3). The statutory period for the assessment of any deficiency or the determination of any refund attributable to this report shall not expire before the expiration of one year from the date the department is notified by the taxpayer or the Internal Revenue Service, whichever is earlier, of the report in writing. Before the expiration of this one-year period, the department and the taxpayer may agree in writing to the extension of this period. The period so agreed upon may be further extended by subsequent agreements in writing made before the expiration of the period previously agreed upon. (c) Whenever, in the opinion of the department, it is necessary to examine any federal income tax return of any taxpayer or any determination, assessment, or report related thereto, the department may compel the taxpayer to produce for inspection a copy of any federal return, copies of all statements and schedules in support thereof, and copies of all determinations, assessments, and reports related thereto.