content percentage means the percentage of the total cost of the bill of materials of the eligible component that is attributable to materials and components that were produced in the United States. (iii) Documentation rules (I) Recordkeeping No domestic content bonus credit shall be determined under this subparagraph unless the taxpayer provides documentation supporting the domestic content percentage (in such form and manner as the Secretary shall prescribe). (II) Certification by unrelated party In the case of materials or components provided to the taxpayer by an unrelated party, the Secretary shall accept certification (in such form and manner as the Secretary shall prescribe) by such unrelated party that the materials or components were produced in the United States. (4) Phaseout (A) In general In the case of any eligible component sold after December 31, 2029, the amount determined under this subsection with respect to such component shall be equal to the product of— (i) the amount determined under paragraph (1) with respect to such component (determined without regard to this paragraph after the application of paragraphs (2) and (3)), multiplied by (ii) the phaseout percentage under subparagraph (B). (B) Phaseout percentage The phase out percentage under this subparagraph is equal to— (i) in the case of an eligible component sold during calendar year 2030, 75 percent, (ii) in the case of an eligible component sold during calendar year 2031, 50 percent, (iii) in the case of an eligible component sold during calendar year 2032, 25 percent, (iv) in the case of an eligible component sold after December 31, 2032, 0 percent. (c) Definitions For purposes of this section— (1) Eligible component (A) In general Except as provided in subparagraphs (B) and (C), the term eligible component means— (i) an approved generic drug, (ii) a licensed biosimilar, and (iii) any drug substance, intermediate, raw material, starting material, reagent, component, in-process material, inactive ingredient, container closure system,