01
The registration, in full, with the promoter's name as it appears on it
It is the one fact about a project that a third party has recorded and that you can verify without the seller's help. Everything else on a brochure is the seller's own account.
The document that settles it
The registration certificate, and a search for that number on the register of the state the land is in.
How this line is commonly presented misleadingly
"RERA approved" with no number, a number too short to search, or a promoter name on the brochure that differs from the one on the certificate. The certificate's promoter is the legal entity; the trading brand often differs.
