The IT Act has provided four dates and the percentage of advance tax to be paid on each of these dates.
If by chance you have paid the excess advance tax you would receive a refund subject to section 237 of
the Income Tax Act with 6% interest per annum on the excess amount subject to Section 244A of the Act
if the excess is more than 10% of the tax liability. If on March 15, you find that you have a shortfall of
advance tax to be paid you can still pay the advance tax before 31 st March and the same would be
treated as advance tax.