of 1986 is amended— (1) by striking retroactive changes in plan .—A stock bonus and inserting “ plan amendments .— (1) Certain retroactive changes in plan A stock bonus , and (2) by adding at the end the following new paragraph: (2) Adoption of plan If an employer adopts a stock bonus, pension, profit-sharing, or annuity plan after the close of a taxable year but before the time prescribed by law for filing the employer’s return of tax for the taxable year (including extensions thereof), the employer may elect to treat the plan as having been adopted as of the last day of the taxable year. . (b) Effective date The amendments made by this section shall apply to plans adopted for taxable years beginning after December 31, 2018. 202. Modification of nondiscrimination rules to protect older, longer service participants (a) In general Section 401 of the Internal Revenue Code of 1986 is amended— (1) by redesignating subsection (o) as subsection (p), and (2) by inserting after subsection (n) the following new subsection: (o) Special rules for applying nondiscrimination rules To protect older, longer service and grandfathered participants (1) Testing of defined benefit plans with closed classes of participants (A) Benefits, rights, or features provided to closed classes A defined benefit plan which provides benefits, rights, or features to a closed class of participants shall not fail to satisfy the requirements of subsection (a)(4) by reason of the composition of such closed class or the benefits, rights, or features provided to such closed class, if— (i) for the plan year as of which the class closes and the 2 succeeding plan years, such benefits, rights, and features satisfy the requirements of subsection (a)(4) (without regard to this subparagraph but taking into account the rules of subparagraph (I)), (ii) after the date as of which the class was closed, any plan amendment which modifies the closed class or the benefits, rights, and features provided to such closed class does not discriminate significantly in favor