partial payment by installments, (B) a conditional sale, or (C) a chattel mortgage arrangement wherein it is provided that the sales price shall be paid in installments, there shall be paid upon each payment with respect to the article a percentage of such payment equal to the rate of tax in effect on the date such payment is due. (2) Sales of installment accounts If installment accounts, with respect to payments on which tax is being computed as provided in paragraph (1), are sold or otherwise disposed of, then paragraph (1) shall not apply with respect to any subsequent payments on such accounts (other than subsequent payments on returned accounts with respect to which credit or refund is allowable by reason of section 6416(b)(5)), but instead— (A) there shall be paid an amount equal to the difference between— (i) the tax previously paid on the payments on such installment accounts, and (ii) the total tax which would be payable if such installment accounts had not been sold or otherwise disposed of (computed as provided in paragraph (1)), except that (B) if any such sale is pursuant to the order of, or subject to the approval of, a court of competent jurisdiction in a bankruptcy or insolvency proceeding, the amount computed under subparagraph (A) shall not exceed the sum of the amounts computed by multiplying— (i) the proportionate share of the amount for which such accounts are sold which is allocable to each unpaid installment payment, by (ii) the rate of tax under this chapter in effect on the date such unpaid installment payment is or was due. The sum of the amounts payable under this subsection in respect of the sale of any article shall not exceed the total tax. 5904. Exemption from tax