Amount (percentage )of stamp duty to be paid for transfer

1. Stamp duty differ from State to State, it is same as of conveyance deed in Delhi, find out from a local lawyer in your case.

2. Consult a local lawyer for all other questions. 

Bedore answering your query, you need to prrovide the following details:

1. Did you buy the flat?

2. Under what circumstanes your mother's name got included in the Registered Document?

3. Have you any brothers and sisters?

(1),(2) &(3) Stamp duty @3% is leviable for a gift deed, on 50% of the value of the flat, (4) Society NOC not necessary, (5) Transfer fee need not be paid, (6) consultant a practicing advocate..

@ R.Ramachandran sir, 1) Yes i had purchased the flat .Complete amount is paid by me, from my account. 2) I use to be out of India.Since the builder was taking a long time to complete the construction and delaying the work, on my behalf to follow up with the builder during that time did the registration jointly in both our name. 3) Yes i have one younger brother.

Dont adopt the GIFT Route.  It will involve unnecessary and avoidable stamp duty.

Instead, ask your mother to give a Registered Relinquishment Deed in your favour, clearly mentioning in the said Deed, that the entire cost of the flat was paid by you, and that her name was included by you purely due to your love and regard for her and that she is now willingly, voluntarily relinquishing her interest, share and title in the 50% of the property in your favour.

This will involve very very nominal stamp duty and registration charges.