After you pay the stamp duty, it is dated, signed by the parties and attested (where required) by witnesses, and then lodged for registration under The Registration Act, 1908 after payment of the registration fee. The registration is carried out by the Sub- Registrar of Assurances of the jurisdiction, where the property is purchased.
All parties signing the instrument are required to be present at the office of the concerned Sub- Registrar of Assurances, either by themselves or through their constituted attorney under a power of attorney to admit execution of the instrument. A passport size photograph, original power of attorney, personal identification such as passport or income tax, PAN Card, adequate photocopies of the original instrument are some of the essentials required for registration. After lodging an instrument, it is registered, and a seal of the Sub-Registrar is affixed on the instrument, thereafter the original instrument is returned to the parties.
The basic purpose of registration is to record execution of document i.e. the record of the ownership of the property, in case of Sale Deed/any Title Deed execution. As long as the title deeds in your name are not registered or recorded, you are not officially the legal owner of the property.