Exemption under section 54F can not exceed the amount of long term capital gains. Although you can either get exemption of entire LTCG if you invest your entire net sales consideration in another residential house property, OR you can get proportionate exemption for the amount invested in the new house where only a part of net sales consideration is invested.
Exemption u/s 54F of Capital Gain, Tax filing, Income tax filing This page explains about the exemption u/s 54F of Capital Gain.
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