is estimated by the Secretary as being equal to the portion of the amount which would be treated as allowed under subpart C of part IV of subchapter A of chapter 1 for the taxable year under section 24(d) by reason of such month being a qualifying month if— (A) the status of the taxpayer as a taxpayer described in section 24(d) is determined with respect to the reference taxable year, (B) the taxpayer's modified adjusted gross income for the taxable year is equal to the taxpayer's modified adjusted gross income for the reference taxable year, (C) unless otherwise determined by the Secretary based on any information known to the Secretary, the only qualifying children of such taxpayer for such month are the qualifying children of such taxpayer for the reference month, and (D) unless otherwise determined by the Secretary based on any information known to the Secretary, the ages of such children (and the status of such children as qualifying children) are determined for such month by taking into account the passage of time since such reference month. (2) Reference taxable year