0 Occupation / Completion Certificate (OC)- is mandatory for builder before giving possession

Check this video recorded from a tv show-

As per video- without OC- the tax is not applicable. If builder give possession without OC, take it in written from builder.

As per THE PUNJAB APARTMENT OWNERSHIP ACT, 1995- It is also mandatory- you can download the document - [Download] from http://puda.nic.in.
On page 13 point - 7- read carefully, it is --
[from document- 
(7) After making such enquiry as may be necessary and satisfying itself that the
occupation certificate has been obtained from the authority required to do so under
any law and that the applicant has done what he is required to do under the
agreement, the competent authority shall issue a certificate to the registering officer
that it is a fit case for enforcing registration and direct the applicant to present the
conveyance deed of apartment, the endorsement on the conveyance deed of
apartment or the sub-lease, as the case may be, though not executed by the other
party, for unilateral execution of registration.]