"When you go in for reforms, you must never blink. If you blink you get derailed," Arun Jaitley said today.
The GST, India's most ambitious tax reform, replaces an unwieldy patchwork of tariffs and creates a single economic zone with common indirect taxes - something that neither the European Union nor the United States can boast.
Companies will be allowed to file late returns for the first two months so that they can adapt to a new online filing system. The strict GST filing timetable will apply from September.
The government has said GST could add two percentage points to economic growth.
There will be four tax slabs - 5, 12, 18 and 28 percent.
More than 6.5 million businesses have already signed up for the GST, Arun Jaitley said earlier this week, pointing that that's more than four-fifths of those already registered to pay India's old business taxes.
With company owners using their personal tax numbers to comply with the GST, the government expects income tax dodgers to have to come clean. Only around 3 percent of people in India pay income tax.
The GST was proposed by the previous Congress-led government of Dr Manmohan Singh, but it was stalled by political gridlock over basics of the proposal including how tax revenue would be collected and divided between the states and the centre.