Gift Tax

I am an NRI. My mother wishes to gift her flat in Indore to my wife who is also an NRI. What sort of tax implication would we (She and I have)?IDo we have to pay any gift tax? if so w hat % of value? We have not paid any taxes in India ever as we have been living out of India for the last several decades. Pls. help clarify to gucciraja @ yahoo.com