(a) General rule. Except for purposes of chapter 24 (relating to the collection of income tax at source on wages), whenever subchapter E begins or ceases to apply to any State (i.e., a State agreement begins or ceases to be effective) as of any January 1, such commencement or cessation of applicability shall apply to taxable years of individuals beginning on or after such date. For example, if subchapter E begins to apply to a particular State on January 1, 1980, it would become applicable for calendar year 1980 for calendar-year taxpayers in that State; but if a taxpayer in the State is using a fiscal year running from July 1 to June 30, the subchapter would begin to apply (except for purposes of chapter 24) to that taxpayer on July 1, 1980, for his taxable year ending June 30, 1981. Similarly, if the subchapter ceases to apply to such State on January 1, 1982, it would cease to apply to calendar-year taxpayers after the end of calendar year 1981; but it would cease to apply (except for purposes of chapter 24) to fiscal-year taxpayers at the end of their fiscal years which are in progress on January 1, 1982. The cessation of applicability of subchapter E to a State does not affect rights, duties, and liabilities with respect to any taxable year for which subchapter E does apply with respect to any taxpayer (or his employer).

(b) Special rules pertaining to withholding—(1) Subchapter E beginning to apply. The Federal withholding system provided in chapter 24 shall go into effect for State individual income tax purposes with respect to wages paid on or after the January 1 as of which subchapter E begins to apply to a State. If an employee is subject to a qualified tax imposed by the State, such withholding system shall apply to his wages paid on or after that January 1, without regard to whether he is a calendar-year or fiscal-year taxpayer. See § 301.6363-3 with respect to transition-year rules.

(2) Subchapter E ceasing to apply. The Federal withholding system provided in chapter 24 shall cease to be effective for State tax purposes with respect to wages paid on or after the January 1 as of which subchapter E ceases to apply to the State, although fiscal-year taxpayers of that State continue to be subject to the other provisions of subchapter E for the remainder of their fiscal years then in progress. See § 301.6363-3 with respect to transition-year rules.