Calculating capital gain

I bought a house in 2006 for 50 lakhs. Even though i paid full 50 lakhs(through bank loan) i had registered the property as per guidance value which was around 30 lakhs.

Now if i sell the house, which amount will be taken into consideration as buying price for calculating capital gain

1. As registered for 30 lakhs..this will be considered

or

2. As i paid 50 lakhs for the property, can this be produced if i produce proper evidence(bank statement, home loan docs etc)

PLease let me know which one will be cinsidered.

Thanks,

Santhosh