Capital Gain Tax on sale of property

Can anyone guide about the following scenario.
A father bought a pot in name of two sons. Both sons are shareholders of the said property i.e. 50%. Now one son (A) wants to sale his share to his brother that is the 50% shareholder also.
A is a tax filer. When plot was purchased, A showed it in his tax return as share from his father at zero cost.
Now how A need to enter the transfer transaction in his return. Firstly cash will increase and what will be its second effect to balance the return.
How capital gain needs to be calculated?

Thanks

First of all some taxes are time bound & if a property is sold after 3 years, some taxes become zero.
Pls call our tax lawyer Mr. Usman & give him my reference… Mohammad Yousaf…
He will tell you the most recent at FBR.
Tell him all your scenario to get best advice.
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Thank you Sir for your reply

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