1st Installment - on or before the 15th day of the month of August that relevant year
2nd Installment - on or before the 15th day of the month of November that relevant year
3rd Installment - on or before the 15th day of the month of February that next year
4th Installment - on or before the 15th day of the month of May that next year
Final Payment - on or before the 30th day of the month of September that next year
Discount on Income Tax payable by Individuals
Any individuals who makes any quarterly self-assessment income tax payment, one month before the due date, is entitled to a 10% discount thereon (not exceeding such percentage on the instalment based on the current year profits).
When you want to make an appeal to tax commission of Sri lanka, there are certain rules to be followed.these Rules may be cited as the Tax Appeals Rules, 2012 which is gazetted by an extra ordinary gazette No. NO. 1760/4 - MONDAY, MAY 28, 2012
(a) An appeal to the Commission under the Act, shall be made in the form of a petition.
(b) A petition shall contain the following particulars
(i) name and address of the petitioner ;
(ii) Tax File Number ITax Payers Identification Number ;
(iii) Commissioner-General's Determination Number and Date ;
(iv) the nature or the type of the tax involved ;
(v) Assessment NumberICharge Number and Date ;
(vi) the total tadcharge, as determined by the Commissioner-General and the penalty imposed ;
(vii) a plain and concise statement of the grounds or reasons on which the appeal is being made and such statement to be set forth in duly numbered paragraphs ;
(viii) the relief claimed ; and (ii) the name and address of an authorized representative, if any.
Please visit the gazette for further details here - LINK