Who coined good & simple tax?
It turns out that well-known tax expert Satya Poddar used this phrase to reiterate

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In his address at the Central Hall of Parliament on Friday to mark the launch of the goods and services tax (GST), Prime Minister Narendra Modi delivered a catchy phrase to describe the indirect taxes reform initiative. He described GST as the good and simple tax. A few minutes later the audio-visual presentation made at the roll-out function also described GST as the good and simple tax. Who coined this catchy phrase for GST? It turns out that well-known tax expert Satya Poddar used this phrase to reiterate what GST must stand for. And he did so in one of his articles published in Business Standard. The headline of Poddar’s article published on May 18, 2015, said : “GST should be a good and simple tax.”