; and (II) ending on the date the failure is corrected. (C) Minimum penalties where failure discovered Notwithstanding clauses (i) and (ii) of subparagraph (D): (i) In general In the case of 1 or more failures with respect to an individual— (I) which are not corrected before the date on which the plan receives a notice from the Secretary of such violation; and (II) which occurred or continued during the period involved; the amount of penalty imposed by subparagraph (A) by reason of such failures with respect to such individual shall not be less than $2,500. (ii) Higher minimum penalty where violations are more than de minimis To the extent violations for which any person is liable under this paragraph for any year are more than de minimis, clause (i) shall be applied by substituting $15,000 for $2,500 with respect to such person. (D) Limitations (i) Penalty not to apply where failure not discovered exercising reasonable diligence No penalty shall be imposed by subparagraph (A) on any failure during any period for which it is established to the satisfaction of the Secretary that the person otherwise liable for such penalty did not know, and exercising reasonable diligence would not have known, that such failure existed. (ii) Penalty not to apply to failures corrected within certain periods No penalty shall be imposed by subparagraph (A) on any failure if— (I) such failure was due to reasonable cause and not to willful neglect