If revision shall be made of a combined return under section 12-223a for the purpose of the tax of two or more corporations, or of an assessment based upon such a return, the Commissioner of Revenue Services shall have power to readjust the taxes of each taxpayer included in such return, or, if revision is made of a return or an assessment against a taxpayer which might have been included in a combined return when the tax was originally reported or assessed, the Commissioner of Revenue Services shall have power to resettle the tax against such taxpayer and any other taxpayers which might have been included in such report upon a combined basis, and shall adjust the taxes of each such taxpayer accordingly.