(1) A taxpayer required to file a return under this act may be required to furnish a true and correct copy of any return or portion of any return filed under the provisions of the internal revenue code.

    (2) A taxpayer shall file an amended return with the department showing any alteration in or modification of a federal income tax return that affects its business income tax base or modified gross receipts tax base under this act. The amended return shall be filed within 120 days after the final determination by the internal revenue service.