you can execute gift deed for 50 per cent share in flat in name of your father in law

2) gift deed should be duly stamped and regsitered

you have to pay 5%stamp duty . if you are gifting 50 per cent share in flat to father in law

2) registration charges would be 1%on market value of flat or Rs 30,000 which ever is less .

3) approximate stamp duty and registration charges would be around Rs 1 lakh

I purchased a flat from my wife. Now I'm owner of flat. I want to make my Father in law co owner of this flat. Kindly let me know how can I execute this.

You have to either sell a portion of property in his name or may even execute a registered gift deed.

This will ensure he to be a joint owner of this proerty.

Flat value is roughly 35 lacs. Flat is in Ambernath (421501) district Thane . How much stamp duty and registration fees approximately it would be to execute this gift deed.

Registration fee and the stamp duty issues are local you may clarify the same from local registrar's office.