So instead of a single flat rate, in the new system, laid out in meticulous detail in a 213-page guide, there are rates of 5, 12, 18 and 28 percent. There are also many exceptions.

Take wood, for instance. In its various manifestations, wood finds its way into every tax bracket. There is a 5 percent tax on wood chips and particles, for example, while the rate is 18 percent on sawed lumber.

Tax rates can also vary depending upon the wholesale price. For example, the kurta shirts at Rizwan Siddique’s air-conditioned store in Crawford Market in Mumbai are to be taxed at 5 percent if their price is under 1,000 rupees, or $16, and 12 percent if they are priced higher.

Add to that a requirement that businesses make 37 online filings a year, and it is not hard to see why some businesses are complaining.

Santosh Dalvi, a partner at KPMG India, an accounting firm, said confusion was widespread. “Things have become very unmanageable, everywhere,” he said, adding: “There are a lot of open areas, a lot of gray areas. From a business perspective, people need to take a decision. It’s becoming quite challenging.”

Others say that in a country as complex as India, it is unrealistic to expect a simple tax system.

“If we came out with one flat tax on everything, there would have been protests in the streets,” said Archit Gupta, founder and chief executive of ClearTax, one of India’s biggest companies selling software to file tax returns online. “We’re such a complex country.”

Given the stark inequality in India, taxes on items used by the poor need to be lower than luxury items, Mr. Dalvi said. So carbonated drinks that only the middle and upper classes can afford are taxed at 28 percent under the new system, with an additional 12 percent levy. Tea and coffee, consumed by rich and poor alike, are taxed at 5 percent.