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.
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
Use prior-year liability or current-year forecast.
Estimator only
Equal split of one annual figure. No mid-year revision or payment tracking.
This is one piece of your return. See which schedules you file, which reliefs apply, and what the whole year comes to.
See your full profileSET 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 November 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).
Related calculators
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.