This is an official work for which the formalities vary with each Municipality. 

In general death certificate and title deed is enough for this. 

You have to make application for mutation of property in your name 

2) enclose copy of sale deed 

3) latest receipt of payment of property taxes 

4) consent of the seller 

5) if no objections are received mutation would be done in your name 

1. File an simple application with the Municipal Assessment dept., duly annexed with the Notarized copy of the Purchase Agreement (Stamp Duty paid & Registered), and an Affidavit and request for Transfer /Mutation of your name in their Records & Registers.

Keep Smiling .... Hemant Agarwal
VISIT: www.chshelpforum.com

You should have applied  for mutation of revenue records at the time of purchase of the property with the help of builder.

As per the revenue records the builder would be ther owner of the property hence  on the basis of the available documentary evidences you may submit an application to the Municipal authority seeking to transfer the property records to your name on the basis of the registered sale deed  held in your possession.

The exact mutation process differs in each state. Please contact a local lawyer who deals with such matters.

- As per law, when the said flat registered in your name , then legally you become the owner of the same.

- However , for the purpose of tax payment , you can register that flat in the government record after getting Mutation.

- The following documents are generally needed for apply for getting Mutation 

1. Application for Mutation 

2. Copy of Sale deed 

3. Affidavit of stamp paper

4. Property tax receipt 

5. Address and identity proof of the applicant.