(a) If a taxpayer's accounting period for Federal income tax purposes is changed, the taxable year and accounting period for which the taxpayer's report is filed under article 9-A of the Tax Law must be changed at the same time to coincide with the new Federal income tax accounting period and taxable year. (See section 6-1.2 of this Title—Short-period reports.)

(b) Where a taxable year or accounting period of less than 12 months results from a change of accounting period, the taxpayer must file a report and pay the tax due for the period beginning from the close of the last taxable year or accounting period for which a report was required to be filed to the date designated as the close of its new accounting period or taxable year. Where a change in taxable year from or to a 52-53 week accounting period, or from one 52-53 week period to a different 52-53 week period, results in a period of either 359 days or more or 6 days or less, the tax for the 359-day-or-more period must be computed as if it were a full taxable year, and the period of six days or less must be added to and deemed part of the following taxable year. In the case of a period consisting of more than 6 days and less than 359 days, a report must be filed for such period.

(c) A taxpayer whose accounting period is changed for Federal income tax purposes is not required to apply for or obtain permission to make a similar change with respect to reports required under article 9-A. In such a case, however, the taxpayer must submit, with the first report filed for the new accounting period under article 9-A, a copy of the consent of the Commissioner of Internal Revenue to the change for Federal income tax purposes. A taxpayer which changes its accounting period for Federal income tax purposes without the prior approval of the Commissioner of Internal Revenue must submit, with the first report filed for the new accounting period under article 9-A, a statement indicating the authority for the Federal change.

(d) In the case of a taxpayer which has an established accounting period for Federal income tax purposes, no change of accounting period for purposes of article 9-A (other than one required by reason of change of the Federal accounting period as set forth in subdivision [a] of this section) will be permitted.