Economy In his words: Why Pranab Mukherjee imposed the controversial retro tax Updated : August 31, 2020 07:03 PM IST In his book, The Coalition Years, the former president wrote about why he chose to implement the controversial retro tax. Subscribe to Moneycontrol PRO at just Rs.33/- per month for the first year. Use code SUPERPRO. Limited period offer. Available on Web and Android.