What is the point at which a buyer becomes a defaulter?

Any violation of the RERA Act’s provisions is punishable. The penalty for each subsequent period of default may total up to 5% of the cost of the plot, apartment, or building, as determined by your respective state authority.
Homebuyers would be subject to a penalty for each day of default, which could total up to 10% of the cost of the plot/apartment, or to imprisonment for up to one year, or to both.