Hi Streamlit Community! 
I wanted to share a practical FinTech utility web app I built for working professionals, job seekers, and graduates in Sri Lanka:
Live App: https://sri-lanka-salary-tax-simulator.streamlit.app
GitHub Repo: GitHub - rasindupramith-oss/sri-lanka-salary-tax-simulator: Interactive Sri Lanka salary, APIT income tax (2025/2026 IRD rules), and EPF/ETF take-home pay simulator built with Streamlit and Plotly. · GitHub
The Problem It Solves
With recent macroeconomic reforms and revised personal income tax (APIT) progressive slabs in Sri Lanka, employees frequently struggle to calculate their exact take-home pay and often misunderstand marginal tax brackets (thinking an entire salary is taxed at the highest bracket rate).
What the App Does
- Official Tax Calibration: Formulated with official Inland Revenue Department (IRD) progressive tax tables for the 2025/2026+ assessment years (including the Rs. 150,000/month tax-free personal relief).
- Interactive Cashflow Waterfall: Built an interactive Plotly Waterfall chart visualizing the flow from Gross Salary → Employee EPF (8%) → APIT Tax → Net In-Pocket Cash.
- Retirement Fund Tracking: Automatically computes statutory employer contributions (12% EPF + 3% ETF) to reveal total monthly retirement wealth accumulation.
- Monthly vs. Annualized View: Users can toggle between monthly budgeting and full 12-month wealth projections.
- Custom Styling: Injected custom CSS to give Streamlit’s native metric cards a modern, dark-mode FinTech aesthetic.
Built using Streamlit, Plotly, and Pandas.
Would love to hear your feedback on the UI and features!