Advance tax is to be paid on all incomes. Therefore, it is payable on capital gain also. However, as the capital gain can not be estimated in advance, advance tax is paid on all capital gains when they arise in the immediately next advance tax due date.

Interest on late payment of Advance Tax:
Interest on late payment of Advance Tax is governed by sections 234 A, 234 B and 234 C.

Interest under section 234A – Default in furnishing the return of Income:
If an assessee has not filed the return of income within the due date, a simple interest @ 1% for every month or part of a month shall be payable. It is calculated from the due date to date of furnishing the return.

Example:
A company files its return on 15th December. Due date of filing return of income is 30th September. Let us assume that the tax payable by the company is Rs.1,00,000. Interest will be calculated as follows:

Tax Liability Rs. 1,00,000/-

Delay = 3 months ie October, November and December.

Interest payable = Rs.1,00,000 X 3%= Rs. 3,000/-

Interest under section 234B- Default in payment of Advance Tax:
If an assessee who is liable to pay advance tax , but not paid the same or or if the advance tax paid by him is less than 90% of the assessed tax, he is liable to pay simple interest at 1% every month or part of a month.

Interest is calculated from April 1st of the next financial year to the date of determination of total income under Section 143 (1). But, if regular assessment u/s. 143 (3) is completed, then interest is charged up to the date of regular assessment.

Interest shall be calculated on the amount equal to the assessed tax in case no advance tax is paid, or on the amount by which the advance tax paid falls short of the assessed tax.

Example:
Mr. X has a tax liability of Rs. 5,00,000/-. TDS Rs. 1,00,000/-
Advance tax payment made by Mr. X for the year is as below:-
15th Sept 2012 Rs. 25,000/-
15th Dec  2012 Rs. 50,000/-
15th Mar  2013 Rs. 25,000/-

Total advance tax paid Rs.1,00,000 /-

Interest u/s 234B is calculated as follows:
Tax on income Rs. 5,00,000
Less TDS         Rs. 1,00,000
                          ————
Assessed tax     Rs. 4,00,000

90% of assessed tax = 400000 X 90% = Rs. 3,60,000 /-

Advance tax paid by Mr. X – Rs.1,00,000 /-

Since there is a shortfall in payment of advance tax, Sec 234B is attracted.

Shortfall = Rs. 3,60,000– Rs. 1,00,000 = Rs.2,60,000/-
(Shortfall means difference between assessed tax and advance tax paid).

Interest under section 234 B = 260000*1%*4 months (Apr-July) = Rs.10,400 /- 

Interest under section 234C
If the advance tax paid is in underestimated instalments or if it s not paid at all, Section 234C gets attracted.

Interest is calculated on the difference between the instalment paid and instalment payable. Rate of interest is @ 1% p.m. for a period of 3 months for every deferment. But, for last instalment on 15th March, interest would be 1% for 1 month only.

Example:
Mr. X gives the following details:
Tax liability on total income Rs. 5,00,000/-
TDS = Rs. 1,00,000
Payment of advance tax:
15 Sept 2012           Rs.  50,000/-
14 Dec  2012           Rs.1,00,000/-
15 Mar  2013           Rs.1,50,000/-
Total advance tax paid Rs.3,00,000/-

Solution:-
Tax liability Rs. 5,00,000
Less TDS Rs. 50,000
Assessed tax Rs.450000 [ 5,00,000 minus 50,000]

Interest u/s 234C is computed as under:

Sept 15
30% of 4,50,000 = 135000 minus 50000 ie; Rs. 85,000 short paid
Interest = 85,000*1% X 3months = 2,550/-

Dec 14
60% of 4,50,000 = 2,70,000 minus 1,50,000/- = Rs. 1,20,000/- paid short.
Interest = 1,20,000*1% X 3months = 3,600/-

15 Mar
100% of 4,50,000 = 450000 minus 3,00,000 = Rs. 1,50,000 /- paid short
1,50,000 X 1% X 1month = Rs. 1500/-
Total Interest payable u/s. 234C is Rs. 2,550+ 3,600+ 1,500 = 7,650/-