are treated as a single employer for purposes of this section have the same taxable year, the taxable years taken into account shall be determined under principles similar to the principles of section 1561. (4) Waiver by Secretary In the case of a failure which is due to reasonable cause and not to willful neglect, the Secretary may waive part or all of the tax imposed by subsection (a) to the extent that the payment of such tax would be excessive relative to the failure involved. (d) Tax not To apply in certain cases This section shall not apply in the case of— (1) any failure of an employer to meet the requirements of subsection (a) with respect to any employee if the failure with respect to such employee occurred during the calendar year immediately following a calendar year during which all employers maintaining such plan normally employed 10 or fewer employees on a typical business day, (2) any governmental plan (within the meaning of section 414(d)), (3) any church plan (within the meaning of section 414(e)), or (4) employers that have not been in existence for three years, taking into account all predecessor employers. (e) Liability for tax The employer shall be liable for the tax imposed by subsection (a) on a failure. All employers, determined without regard to subsection (f)(2), shall be jointly and severally liable for the liability of any other employer with which they are aggregated under subsection (f)(2). (f) Definitions For purposes of this section— (1) the term automatic contribution plan has the meaning given such term under section 414(aa), and (2) the term employer includes all employers treated as a single employer under subsection (b), (c), (m), or (o) of section 414. . (c) Clerical amendment The table of sections for chapter 43 of the Internal Revenue Code of 1986 is amended by adding at the end the following new item: Sec. 4980J. Failure to maintain automatic contribution plan. . (d) Effective date (1) In general The amendments made by subsection (a) shall apply to years beginning after