transferor’s maximum tax liability
(4) Transferor’s maximum tax liability The term “transferor’s maximum tax liability” means, with respect to the disposition of any interest, the sum of— (A) the maximum amount which the Secretary determines could be imposed as tax under section 871(b)(1) or 882(a)(1) by reason of the disposition, plus (B) the amount the Secretary determines to be the transferor’s unsatisfied withholding liability with respect to such interest.