Sri Lanka Bonus Tax Calculator — APIT on Lump-Sum Payments (2025/26)

A bonus is taxed differently from your regular monthly salary because it stacks on top of the income you have already earned in the year. The Inland Revenue Department's APIT Table 02 — “Rates for the Deduction of Tax from Lump-Sum Payments to Resident Employees” — prescribes a four-step differential calculation that this page implements line for line.

1. Annualise regular employment income: A_reg = M × 12 + Σ prior lump sums (same Y/A). The prior-lump-sums term matters when a second bonus is paid in the same year — without it the second bonus is under-withheld.
2. Compute the annual APIT on that figure using Table 01: T_before = apit_annual(A_reg).
3. Add the new lump sum to annual income and re-compute: T_after = apit_annual(A_reg + L).
4. Withhold the difference: T_lump = T_after − T_before.

The annual brackets that apit_annual() walks are those set by the Inland Revenue (Amendment) Act No. 2 of 2025, effective 1 April 2025. Income up to Rs 1,800,000 per year is exempt as personal relief; above that, the progressive ladder is:

• Rs 0 → Rs 1,000,000 : 6%
• Rs 1,000,000 → Rs 1,500,000 : 18%
• Rs 1,500,000 → Rs 2,000,000 : 24%
• Rs 2,000,000 → Rs 2,500,000 : 30%
• Above Rs 2,500,000 : 36%

Why the marginal rate, not the effective rate, drives bonus tax

Your regular salary's effective tax rate (total APIT ÷ annual gross) is always lower than your top bracket because the lower brackets keep their lower rates. A bonus is different — it sits on top of an already-taxed annualised income, so it is taxed only at whichever bracket(s) the bonus crosses. If you are already a Rs 350,000-per-month earner (annual taxable Rs 2,400,000, in the 30% band), a Rs 200,000 bonus pushes part of you into the 30% band and part into the 36% band — see Example 1 below. If you earn Rs 600,000-per-month you are already in the 36% bracket, so every rupee of bonus is taxed at the full 36%.

Two paths, one answer — how the calculator self-checks

The page runs two independent implementations of Table 02 and reconciles them. The primary method is the annual differential (compute annual tax with and without the bonus, subtract). The secondary is a per-slice bracket walk that integrates the bonus directly across whichever bracket boundaries it crosses, given the taxpayer's pre-bonus annual taxable income as the starting point. The two methods are mathematically equivalent for a piecewise-linear progressive scale, so the on-screen reconciliation dot stays green; if the bracket data ever drifts out of sync, the dot turns amber and the page tells you which figure to trust.

What this calculator does not include

Table 02 governs cash lump sums to resident employees with a single employer. Non-residents are covered by APIT Table 04 — different rates, no Rs 1,800,000 relief. Terminal benefits paid at separation (gratuity, commuted pension, compensation for loss of office) follow Table 03 and its concessionary multi-year averaging — use the Sri Lanka Gratuity Calculator for that. Employees with multiple employers in the same Y/A must reconcile the cumulative position under Table 05; a single-employer calculator over-withholds for them. EPF (8% employee / 12% employer) and ETF (3% employer) typically do not apply to discretionary bonus payments — confirm with your payroll team for your specific contract.

Rounding and presentation

The IRD's payroll convention is to display tax amounts in whole rupees. The calculator performs the bracket walk at full floating precision and only rounds at the display layer; the working table shows the integer-rounded figures. A small (≤ Rs 1) display gap between the differential and the slice-walk methods is normal at fractional inputs and reflects rounding only — the underlying calculation is identical.

Three scenarios that cover the most common Sri Lankan bonus situations, plus an edge case. Try each set of inputs in the calculator above — the working table should match to the rupee.

• IRD — APIT Table 02 (Lump-Sum Payments to Resident Employees), Y/A 2025/26
• IRD — APIT Table 01 (Monthly Tax Deductions from Regular Profits), Y/A 2025/26
• Inland Revenue (Amendment) Act No. 2 of 2025
• IRD — Tax Chart for Y/A 2025/26

The Table 02 method and Y/A 2025/26 brackets above were last cross-checked against the IRD sources on 2026-05-17.