employer with 25 or fewer employees, as determined by substituting 25 for 100 in section 408(p)(2)(C)(i)) . (c) Automatic contribution plan Paragraph (2) of section 45E(d) of such Code is amended by striking a qualified employer plan within the meaning of section 4972(d) and inserting an automatic contribution plan within the meaning of section 414(aa) . (d) Conforming change Paragraph (2) of section 45E(d) of such Code is amended by adding at the end thereof the following: For purposes of this section, the term qualified employer plan has the meaning given such term under section 4972(d). . (e) Effective date The amendment made by this section shall apply to taxable years beginning after December 31, 2017. 9. Small employer automatic enrollment credit (a) In general Subpart D of part IV of subchapter A of chapter 1 of the Internal Revenue Code of 1986 is amended by adding at the end the following new section: 45S. Auto-enrollment credit for retirement savings options provided by small employers (a) In general For purposes of section 38, in the case of an eligible employer, the retirement auto-enrollment credit determined under this section for any taxable year is an amount equal to— (1) $500 for any taxable year occurring during the credit period, and (2) zero for any other taxable year. (b) Credit period For purposes of subsection (a)— (1) In general The credit period with respect to any eligible employer is the 5-taxable-year period beginning with the first taxable year for which the employer adopts an automatic contribution plan (as defined in section 414(aa)), determined without regard to a plan described in section 414(aa)(2)(D) (relating to a grandfathered automatic contribution plan). (2) Maintenance of arrangement No taxable year with respect to an employer shall be treated as occurring within the credit period unless the arrangement described in section 401(k)(14)(C) is included in the plan for such year. (c) Eligible employer For purposes of this section, the term eligible employer has the meaning