New Delhi, Sept. 9 -- The latest rationalisation of GST slabs has sent a quiet but significant signal: tax rates are no longer untouchable. In the past, governments have hesitated to fiddle with tax rates much, on the premise that a bird in the hand is worth two in the bush.

This has been true of both direct taxes-where corporate taxpayers have benefited much more than the individual salaried middle-class taxpayer-and indirect taxes, which fall on the end consumer.

The introduction of the goods and services tax (GST) regime in 2017 replaced a maze of excise and sales taxes with a uniform nationwide tax and eliminated double taxation through input tax credit.

But its success came at a cost: a complex five-slab structure and a costly pro...