Registery of a flat but huge difference between circle value and actual value.

I am Arpan Goenka from Kolkata. We are 12 tenants in building under padgi system from last 30 years. Now landlord wants to sell officially to tenants. Both party agrred @ Rs. 1000 sq feet approx while circle value by state showing Rs. 4500 per sq feet. Hence if tenant pay stamp duty on Rs. 4500 and pay chque of Rs. 1000 then will get IT notice from central govt as per all charted accountant. What is the solution ?