provide, in regulations, the circumstances under which a credit or refund (without interest) of the tax under subsection (a) shall be allowed or made to the person who exported the taxable carbon substance, where— (i) the person who paid the tax waives his claim to the amount of such credit or refund, and (ii) the person exporting the taxable carbon substance provides such information as the Secretary may require in such regulations. 4692. Refunds or credits (a) Sequestered carbon Under regulations prescribed by the Secretary, if— (1) a person uses a taxable carbon substance as a feedstock so that the carbon associated with such substance will not be emitted, or (2) a person captures and sequesters the carbon in a taxable carbon substance, then an amount equal to the amount of tax in effect under section 4691(b) with respect to such substance for the calendar year in which such use begins shall be allowed as a credit or refund (without interest) to such person in the same manner as if it were an overpayment of tax imposed by section 4691. (b) Previously taxed carbon substances used To make another taxable carbon substance Under regulations prescribed by the Secretary, if— (1) a tax under section 4691 was paid with respect to any taxable carbon substance, and (2) such substance was used by any person in the manufacture or production of any other substance which is a taxable carbon substance, then an amount equal to the tax so paid shall be allowed as a credit or refund (without interest) to such person in the same manner as if it were an overpayment of tax imposed by section 4691(a). In any case to which this paragraph applies, the amount of any such credit or refund shall not exceed the amount of tax imposed by section 4691(a) on the other taxable fuel manufactured or produced (or which would have been imposed by such subsection on such other fuel but for section 4691(c)). 4693. Border adjustments (a) Imports The Secretary shall impose a carbon equivalency fee on imports of carbon-intensive goods that shall be