(a) After the expiration of four years from the last day prescribed by law for filing the return for such taxable year determined without regard to any extension of time granted to either spouse. Thus, where an extension of time for filing returns has been granted by the Franchise Tax Board in accordance with Revenue and Taxation Code Section 18567, the extension shall be disregarded in determining the last day upon which a joint return may be filed after separate returns have been filed;

(b) After there has been mailed to either spouse, with respect to such taxable year, a notice of deficiency under Revenue and Taxation Code Section 19033, if the spouse, as to such notice, files a protest under Revenue and Taxation Code Section 19041 or appeal under Revenue and Taxation Code Section 19045 which is still pending;

(c) After either spouse has commenced a suit in any court for the recovery of any part of the tax for such taxable year; or

(d) After either spouse has entered into a closing agreement under Revenue and Taxation Code Section 19441 with respect to such taxable year.