VAT on apartment purchased in 2008

Hello, I purchased a new ( never lived in, new construction) Apartment in 2008 in Mumbai. After all these years , last year my builder is asking all the society members to pay VAT on the purchased property. I heard that the builder is suppose to bear this amount . Also I feel the amount he is asking is on a very high side . What I feel is fishy is that he is willing to offer a discount of over 30% on the VAT he is asking . I do not want to pay him anything , please suggest how do I proceed to reply him formally . Thanks