Capital Gains Tax on Property Sale

Bought a property in 2012 for 18 lakhs, 

Now, selling it for 32 lakhs on Agreement for Sale, where buyer will be paying the amount over a period of 5 years and final formalities of registration etc. will be done after 5 years (2028).

Question: Which year is the capital gains tax applicable? 

1. Over all the 5 years, depending on the amount received each year?

2. In 2028, when the final formalities are done?