Due Date to file income tax return for person other than companies and non Audit case is 31.08.2012 .Many person have not paid their Advance tax in time .By the way advance tax for person other than companies is payable if tax due in a financial year is more than 10000 before the TDS amount .Such person have to pay advance tax in three instalments.
30% of tax assessed =15 September of previous year
60% of tax assessed=15 December of previous year
100% of tax assessed = 31March of previous year
Here tax Assessed means = Tax due minus Tax deducted at sources.
Further for capital gain amount person can pay prospective instalments only.so If you have not paid your tax pro-rata bases in advance as shown above you have to pay interest u/s 234C .Further If you have not paid your full taxes by 31.03.2012 for Ay 2012-13 then you have pay interest under section 234B on balance amount of tax .
Interest U/s 234A is payable only if you miss the Income tax due date for Ay 2012-13 ie 31.08.2012.And I hope you are not interest in calculation under this section .However the given calculator will calculate interest under this section also where ever applicable.
Interest Rate: Interest Rate is 1% per month or part there of in all the above cases