Other plans.
(iv) Other plans. In the case of any other plan, each employee's social security supplement accrues ratably over the period beginning with the later of the employee's commencement of participation in the plan or the effective date of the social security supplement and ending with the earliest age at which the social security supplement is payable to the employee. The effective date of the social security supplement is the later of the effective date of the amendment adding the social security supplement or the effective date of the amendment modifying an existing social security supplement to comply with the requirements of this definition. If, by the end of the first plan year to which these regulations apply, as set forth in 1.401(a)(4)-13 (a) and (b), an amendment is made to a social security supplement in existence on September 19, 1991, the employer may treat the accrued portion of the social security supplement, as determined under the plan without regard to amendments made after September 19, 1991, as included in the employee's accrued social security supplement, provided that the remainder of the social security supplement is accrued under the otherwise-applicable method.