I need to sell my 770 sq ft flat in runwal garden city Phase 2 it is located on 13th floor with stilt parking how much I

HI,
I bought flat in Runwal Garden city Thane- Phase-II, posession awaited 95% payment made to the builder. Since my agreement was made before 1st Apr 2010, builder has demanded 5% vat on agreement value. Is the 5% Vat on agreement value is valid? This is not fare from government to leavy 5% vat on bases of agreement date. I can't see any proper guidelines from government on collection of 5% vat on agreement value. I'm afraid the builder will take advantage of this and collect 5% vat which may not be paid to govt. Is the 5% vat on agreement value is valid? Is there any official document/guidelines declared by govt.? Can we show this guidelines and ask builder to follow the same?