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Income Tax Due Dates in Sri Lanka: Instalments, Final Payment and Return

Pick a year of assessment and the tool lists the income tax due dates for Sri Lanka: four quarterly instalments, the final payment and the return of income, with the weekday and the days left.

Maintained by Hirantha Sandaruwan Lakshan. Rules checked 28 October 2026 against Inland Revenue Department, Guide to fill the Return of Income for individuals 2025/26 and 6 more sources.

About this tool

It also works out each instalment from last year's tax and shows how late payment interest adds up once you type the rate. A year of assessment runs from 1 April to 31 March, so 2026/27 is 1 April 2026 to 31 March 2027.

How it works

The instalments for a year of assessment fall on 15 August and 15 November of its first calendar year, then 15 February and 15 May of the next. For 2026/27 that is 15 August 2026, 15 November 2026, 15 February 2027 and 15 May 2027. The final payment of the balance tax is due on 30 September after the year ends, and the return of income on 30 November. For 2025/26 those are 30 September 2026 and 30 November 2026.

For the instalment amount, the Inland Revenue Department circular for 2026/27 uses (A - C) / B. A is the gross income tax payable, before credits, for the preceding year. C is the tax already paid this year plus credits you expect. B is the number of instalments left, counting the current one. If each earlier instalment was paid in full, the four amounts come out equal. The old Statement of Estimated Tax was removed by the Inland Revenue (Amendment) Act No. 11 of 2026, and the tool uses the standard method only.

For late payment, the tool counts the months from the due date to the day you paid, and a part of a month counts as a month. It multiplies the unpaid amount by the monthly rate you type and by those months, as simple interest. No rate is filled in for you, because the rate has to come from the Act or an Inland Revenue notice. Weekends, public holidays and extensions are not applied, so check the Inland Revenue Department notice for the year. Nothing you type leaves your browser.

Worked examples

Dates for 2026/27

Year of assessment 2026/27 starts on 1 April 2026. The instalments are due on 15 August 2026, 15 November 2026, 15 February 2027 and 15 May 2027. The final payment is due on 30 September 2027 and the return on 30 November 2027.

Instalment from last year's tax

Tax for the preceding year was Rs. 480,000 and nothing has been paid or credited. Each instalment is (480,000 - 0) / 4 = Rs. 120,000. With Rs. 150,000 of credits on tax of Rs. 900,000, the base is 750,000 and each instalment is Rs. 187,500.

Interest if the rate were 1.5% a month

Rs. 120,000 due on 15 November 2026 and paid on 20 December 2026 is 1 month and 5 days late, which counts as 2 months. At 1.5% a month the interest is 120,000 x 1.5% x 2 = Rs. 3,600. The 1.5% is only an example. Use the rate in force.

Dates for a year of assessment that starts in year Y

WhatDateIncome it covers
Instalment 115 August, year Y1 April to 30 June
Instalment 215 November, year Y1 July to 30 September
Instalment 315 February, year Y+11 October to 31 December
Instalment 415 May, year Y+11 January to 31 March
Final payment30 September, year Y+1Balance of the year's tax
Return of income30 November, year Y+1The whole year of assessment

Frequently asked questions

What are the tax deadlines in Sri Lanka?

For income tax, instalments fall on 15 August, 15 November, 15 February and 15 May, the final payment on 30 September and the return on 30 November of the year after the year of assessment starts. Other taxes such as VAT have their own dates, so use the Inland Revenue Department calendar for them.

What is the last date to file income taxes for 2026?

For year of assessment 2025/26, the Inland Revenue Department set the final payment for 30 September 2026, and its guide to the 2025/26 return says to file on or before 30 November 2026. For 2026/27 the return falls on 30 November 2027 if the same pattern holds, which is an inference, so confirm it with the Department when the time comes.

What is the due date for tax payments?

Quarterly instalments are due on 15 August, 15 November, 15 February and 15 May. Any balance is due as a final payment on 30 September after the year of assessment ends. The tool shows each date for the year you pick.

What is the due date for tax?

It depends on the step. Instalments come first, then the final payment on 30 September and the return on 30 November of the following year. Pick the year of assessment in the tool to see all six dates and how many days are left.

How is each quarterly instalment worked out?

The 2026/27 circular uses (A - C) / B, where A is last year's gross income tax before credits, C is tax already paid and credits expected, and B is the instalments left including the current one. With A of Rs. 480,000 and no credits, each instalment is Rs. 120,000.

Is there interest on late income tax?

Yes. The Inland Revenue Department says interest and penalties apply to late payment and that interest cannot be waived or reduced. Daily FT reports the rate as 1.5% per month or part of a month, but this tool does not fill a rate in. Type the rate you have confirmed and it adds up simple interest by the month.

Does a part of a month count as a month?

Yes in the tool, which follows the Daily FT description of interest as per month or part of a month. Paying one day late is one month and paying 35 days late is two months. Check the wording of the Act or the Department notice for your case.

What if a due date falls on a weekend or holiday?

The tool shows the weekday of each date but does not move it. Check the Inland Revenue Department notice for the year, and pay early if the date is a weekend or a public holiday.

Sources & references

Updated Oct 28, 2026