Who is liable to pay Stamp Duty - the buyer or the seller ?

 The liability of paying stamp duty is that of the buyer unless there is an agreement to the contrary. 

In addition, Is it anywhere written in the Indian Stamp Act, that stamp duty has being paid by buyer.

It  depend on the party.

I fully agree with Y. Prakash and wish to add that Section 29 of the Indian Stamp Act, more particularly, section 29 (c)  provides: "In the absence of an agreement to the contrary, the expense of providing the proper stamp shall be borne....(c) in the case of a conveyance (including a re-conveyance of mortgaged property) by the grantee" . Therefore, unless agreed between the buyer and seller otherwise the expenses on stamp duty has to be borne by the buyer of the property. 

Dear Sir,

As per Indian Stamp Act, Stamp Duty is paid by the buyer not paid by the seller.

With Regards

Sanjeev Gupta