What it can do
Your Personal Tax Questions, Answered Step by Step
Do I Need to File?
Whether you must pay tax or submit a return for the year.
Annual Tax
How much tax you owe, with the working shown step by step.
Monthly APIT
How much tax is taken from your salary each month.
Due Dates
Instalments, final payment and return deadlines.
Other Income
Interest, rent, service fees, dividends, and selling land or shares.
Filing Help
Documents to collect, TIN registration, filing on RAMIS and paying.
Ask in Sinhala, English or Singlish. Rules snapshot: October 2026.
No coding needed
Set It Up in ChatGPT or Claude
Pick the app you already use. Menu names can change slightly as the apps update.
Set up in ChatGPT
Easiest to share with family and friends. A paid plan is needed to create a GPT.
- 1
Download the files: click “Get it on GitHub”, press the green Code button and choose Download ZIP. Unzip it.
- 2
In ChatGPT, open Explore GPTs, then Create.
- 3
Open chatgpt/custom-gpt-instructions.md and copy the text under “Instructions” into the Instructions box.
- 4
Upload the files from the references folder, and scripts/lk_tax_calc.py, as Knowledge. Turn on Web Search and Code Interpreter.
- 5
Save, then ask your tax question.
Set up in Claude
Needs a Claude plan that supports Skills.
- 1
Download the files: click “Get it on GitHub”, press the green Code button and choose Download ZIP.
- 2
Make sure the zip contains the lk-personal-tax-skill folder with SKILL.md inside it.
- 3
In claude.ai go to Settings, then Capabilities, then Skills, and upload the zip.
- 4
Start a new chat and ask your tax question.
Developer? Claude Code users can copy the folder to ~/.claude/skills/lk-personal-tax/. See the README for the calculator and layout.
Know the limits
What It Will Not Do
It does not log in to RAMIS or file or pay for you. It explains the steps and you do them.
It never needs your NIC, TIN, bank details or passwords. Do not share them.
It is not a licensed tax advisor. Complicated cases (partnerships, mid-year change of residency, gratuity, foreign tax credits) should go to the IRD or a registered tax advisor.
Rules are a snapshot as at October 2026. Sri Lankan tax law changes often, usually in the November Budget, so confirm important figures at ird.gov.lk.
Tips
Get Better Answers
Say which year you mean, for example “2025/26”. The tax year runs from 1 April to 31 March.
Give amounts per month or per year, and say which.
Keep your salary slip, T-10 certificate or bank interest certificate nearby.
Read the “assumptions” part of the answer, then check the final numbers with the IRD or a tax advisor before you file.
Contribute
Spot an Error? Help Us Fix It
Tax rules change often. If a rate, slab or deadline is out of date, open an issue or pull request on GitHub.
