Property purchased but not shown in return and now sold

If The audit assessee is an individual and the property is self occupied then calculate long term capital gain and pay taxes @ 20%+education cess @ 3%

The transaction of sale of property, which was purchased in FY 2009-10, must be disclosed in the return for AY 2018-19 and tax be paid on long term capital gain if so warranted. Since time for issuing notice u/s 148 to tax undisclosed investment of rupees 3.5 lac has elapsed by now, Income-tax department cannot take any action regarding the investment not disclosed in the return for AY 2010-11. This is my view.

That means we have to pay tax only on capital gain and not on full sale amount of 10 lac

Yes the tax will be paid on capital gain