The Sale price of your flat is Rs. 27 Lakhs. The purchase price of your flat would be indexed and your Indexed Cost of Acquisition would be approx Rs. 19.60 Lakhs (Rs. 7 lakhs*280/100) and therefore your Long Term Capital Gains would be approx Rs. 7.4 lakhs. You will be liable to pay the LTCG tax @ 20.8% on Rs. 7.4 lakhs i.e. Rs. ~1.54 lakhs.
The amount paid by you for purchasing the residential flat can not be offset against capital gains on sale of residential flat because the new flat was not purchased 1 year before -
Exemption under Section 54 is allowed only if :
- The new residential property must be purchased either 1 year before the sale or 2 years after the sale of the property/asset.
Yes, you will have to show the same in ITR.
Any Capital Gain Tax arised during any financial year can be disclosed in the Income Tax Return under Capital Gains Head of income in year of Assessment, and can pay either self assessment tax or adjust against TDS if any.