How this tax calculator works
You tap your income types and enter the numbers you already know — monthly salary, monthly rent, yearly totals for the rest. The calculator adds them into one assessable income, subtracts your Rs. 1.8 million personal relief, and applies the current bands — 6% on the first Rs. 1 million of taxable income, then 18%, 24% and 30% per Rs. 500,000 slab, and 36% above that. It then subtracts every rupee already withheld from you (APIT on salary, 5% AIT on professional fees, 10% on rent, 10% on interest) to show the number that actually matters: what’s left to pay — or what you’re owed back.
What each income source does in the calculation
| Income | How it’s taxed | Tax withheld from you |
|---|---|---|
| Salary | Normal bands; employer deducts monthly APIT | APIT per IRD Table 1 (auto-estimated, or enter your T-10 figure) |
| FD & savings interest | Normal bands — interest is assessable income, and the bank’s deduction is not a final tax | 10% AIT by the bank (creditable) |
| Rent | Normal bands after the automatic 25% rent relief for repairs & maintenance | 10% AIT if your tenant is a company paying over Rs. 100k/month |
| Foreign clients (FX) | Capped at 15% if received in FX and remitted through a Sri Lankan bank; normal bands otherwise | None — foreign clients don’t withhold |
| Self-employment (local) | Normal bands on profit after business expenses | 5% AIT by company clients above Rs. 100k/month |
Sources: IRD Notice PN/IT/2025-01 (rates, relief, 10% interest AIT, 15% cap); Fifth Schedule para 2(c) of the Inland Revenue Act (25% rent relief); IRD Notice PN/IT/2022-03 (5% services / 10% rent AIT); IRD individual return guide (all AIT creditable via Schedule 7).
Quarterly instalments or one annual return?
This is the question multi-income earners get wrong most often, and the calculator answers it for your numbers. The rule of thumb it applies:
- Salary only, fully covered by APIT → no quarterly payments. A return matters mainly when you’re owed a refund.
- Any business, rental, interest or foreign income with tax still owing → you’re an instalment payer: Statement of Estimated Tax, quarterly payments on 15 August, 15 November, 15 February and 15 May, balance by 30 September, return by 30 November.
- Extra income, but your WHT credits cover the bill → instalments would be nil; the annual return reconciles everything and claims any refund.
Worked example: salary + two FDs
Nimal earns Rs. 250,000 a month and his fixed deposits paid Rs. 500,000 interest this year (banks deducted Rs. 50,000):
- Assessable incomeLKR 3,500,000
- Personal relief− LKR 1,800,000
- Taxable incomeLKR 1,700,000
- Tax (1M × 6% + 500k × 18% + 200k × 24%)LKR 198,000
- APIT already deducted (12 × 8,000)− LKR 96,000
- AIT on interest− LKR 50,000
- Balance to pay for the yearLKR 52,000
Because the Rs. 52,000 comes from investment income his employer can’t withhold on, Nimal is an instalment payer — about Rs. 13,000 a quarter. Without the FDs, his APIT alone would have settled everything, monthly.
Want the monthly payslip view instead? Use the salary & APIT calculator. Leaving a job? There’s a gratuity calculator too.
These figures are estimates for a resident individual on Y/A 2025/26 rules, and simplify some edge cases: qualifying payments beyond personal relief, terminal benefits, capital gains, and the fine detail of the 15% FX computation (our method follows the IRD’s SET guide example, as no statutory formula exists). Always confirm your position with a Chartered Accountant or tax practitioner before paying or filing.
Evidence for the rules used
- Relief, slabs, 10% interest AIT, 15% FX cap: IRD Notice PN/IT/2025-01 and the consolidated Inland Revenue Act (First Schedule paras 1 & 1(6))
- 25% rent relief: Fifth Schedule para 2(c) of the consolidated Act; applied in Example 2 of the IRD individual return guide
- Interest & other AIT creditable, not final: IRA ss.88–89 and Schedule 7 of the return guide; 5%/10% AIT rates per PN/IT/2022-03
- 15% cap computation method: IRD Statement of Estimated Tax guide 2025/26, Example 01
- Instalment dates and return deadline: IRD Tax Calendar (IRA ss.90, 93)