Some of the rules of Income Tax are little confuding for me. One such is Section 234 (B, C) for calculation of interest and penalty of non payment of Advance Tax, etc. I found following two links helpful:
Section 234 B: http://www.vakilno1.com/bareacts/incometaxact/s234b.htm . This section is responsible for tax after the financial year is complete. For example; For FY07-08 (1st April, 2007-31st March, 2008); interest from 1st April, 2008 till the date the tax is paid, is calculated. Months are also calculated on partial basis. Example you would be paying interest for 3.76 months.
Section 234 C: http://www.vakilno1.com/bareacts/incometaxact/s234c.htm . This section is used to calculate interest for the delay period in the FY. For example; For FY07-08 (1st April, 2007-31st March, 2008); interest from 15th Sep, 2007 till 15th Dec, 2007 would be calculated if tax was due for 15th Sept but not paid till 16th Dec. Note that till 15th Sept:30% of tax is due, till 15th Dec:60% of tax is due, 15th march: 100% of tax is due.