Retrospective exemption for integrated tax on leased aircraft parts, with refund remedy and limited claim period. Clause deems notification G.S.R. 850(E) amending G.S.R. 785(E) to have been effective from 1 July 2017, giving retrospective exemption from integrated tax on aircraft, aircraft engines and aircraft parts imported under cross-border lease for the specified period. It provides for refunds of integrated tax collected that would not have been payable had the amendment been effective, and requires refund claims to be filed within six months from the date the Finance Bill, 2018 receives presidential assent.