Joint sessions of the two houses of Parliament in India, the Lok Sabha and the Rajya Sabha, are permitted by Article 108 of the Indian Constitution. These sessions typically occur under specific circumstances:

1. Deadlock on a Bill: When a bill is passed by one house but rejected by the other, or if the other house suggests amendments that the originating house does not agree with, a joint session can be called to resolve the deadlock. This also applies if more than six months elapse without the bill being passed by both houses.
2. National Emergency: In rare cases, joint sessions may be convened during a national emergency to discuss and pass critical legislation swiftly.

However, joint sessions are not permitted in certain situations:

1. Money Bills: Joint sessions cannot be called for money bills. These bills can only be introduced in the Lok Sabha and require its approval. The Rajya Sabha can only make recommendations, which the Lok Sabha may choose to accept or reject.
2. Constitutional Amendment Bills: These bills require a separate approval by a two-thirds majority in both houses. Joint sessions are not applicable here as each house must independently agree to the amendments.