Disputed Tax definition clarifies computation and scope for appeals and pending proceedings under the Act. Section 2 defines operative terms for the Act: appellant (taxpayers with pending appeals, writs, DRP objections, or revision applications, excluding Settlement Commission matters); the method for computing disputed tax according to the procedural posture as on the specified date; and related concepts of disputed interest, disputed penalty, disputed fee, and tax arrear, with exclusions for Settlement Commission outcomes and cross-reference to the Income-tax Act for undefined terms.