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Quarterly Income Tax Installment Calculator Sri Lanka

If you're self-employed: estimate your Q1–Q4 installments based on prior-year liability or current-year forecast.

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Self-employed

Reflects Year of Assessment 2025/2026 · Last updated 2026-06-13 · Reviewed by TaxWise · Source: Inland Revenue Act No. 24 of 2017, Inland Revenue Department

Calculator
Self-assessment installments
SET Q1–Q4 for Y/A 2025/2026. Each installment is one quarter of estimated annual tax.
Estimated annual tax payableRs. 240,000

Use prior-year liability or current-year forecast.

Rs. 0Rs. 5,000,000
Result
Rs.60,000
Per quarter (equal split)
Q115 Aug 2025Rs. 60,000
Q215 Nov 2025Rs. 60,000
Q315 Feb 2026Rs. 60,000
Q415 May 2026Rs. 60,000

Estimator only

Equal split of one annual figure. No mid-year revision or payment tracking.

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Deadlines: 15 Aug / 15 Nov / 15 Feb / 15 May for Y/A 2025/2026.
Full experience

SET installments tied to your live liability

As income changes through the year, TaxWise recalculates what each quarterly payment should be.

  • Forecast annual tax from actual income entered so far
  • SET Q1–Q4 deadlines from the active Y/A config
  • Record installments paid and balance due at filing
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Filing opens Apr 2026 · Y/A 2025/2026 return due 30 Nov 2026

Frequently asked questions

When are quarterly tax installments due in Sri Lanka?
15 August, 15 November, 15 February and 15 May. A final balance payment is due 30 September after the year of assessment.
How much is each installment?
One quarter (25%) of your estimated annual tax, per the Statement of Estimated Tax (SET).

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Estimator disclaimer

Results follow the Inland Revenue Act and the 2025 Amendment for Y/A 2025/2026 but are not tax advice. Rounding, missing inputs, and simplified assumptions can change the final figure; only a filed return counts with IRD.