S.45: Capital gains — Long-term capital gains —Allotment letter – – Subsequent letter and premises ownership agreement — Improvement in rights which already created — Date of acquisition of right not date of registration but date of allotment letter — Holding of property more than 36 months — Assessable as long term capital gains – Entitled to Indexation benefit —Entitled to exemption on reinvestment in new flat [ S. 2(42A),54 , 54F ]