Stamp Duty is a tax collected by the Government on every document by which any right, title, interest or liability is created, transferred, extended, extinguished or recorded. Since the values of transactions in the real estate market tend to be quite high, the amount of stamp duty is also a large amount.
Only exception to Stamp Duty is when the property is transferred through "Will" of a deceased person. All other transfer documents like agreement to sell, development agreement, Conveyance Deed, Gift Deed, Mortgage Deed, Exchange Deed, Deed of Partition, Power of Attorneys, lease deeds, etc. have to be properly stamped before registration.