🇱🇰 Sri Lankan Tax Calculator

A Python-based income tax calculator built around Sri Lanka's April 2025 tax reforms. This project demonstrates the use of functions, lambdas, and functional programming concepts (map, filter, zip, sorted) to compute progressive income tax across multiple taxpayers.

---

📋 Tax Brackets (2025 Reforms)

Income Range (Rs.)	Tax Rate
Up to 1,800,000	0%
1,800,001 – 2,800,000	6%
2,800,001 – 3,300,000	18%
3,300,001 – 3,800,000	24%
3,800,001 – 4,300,000	30%
Above 4,300,000	36%

---

✨ Features

• Progressive Tax Calculation — Accurately computes income tax using Sri Lanka's multi-slab system.
• Effective Tax Rate — Shows the actual percentage of income paid as tax.
• Take-Home Pay — Calculates annual and monthly take-home income after tax.
• Taxpayer Ranking — Ranks multiple taxpayers by total tax paid (highest to lowest).
• High Earner Detection — Filters and displays individuals in the top tax bracket (≥ Rs. 4,300,000).
• Summary Statistics — Aggregated metrics including total tax revenue, average effective rate, and average monthly take-home pay.

---

🚀 Getting Started

Prerequisites

• Python 3.6+ (uses f-strings and numeric underscores)

Run the Calculator

python tax_calculator.py

---

📂 Project Structure

Tax-cal/
├── tax_calculator.py   # Main application with all tax logic and reporting
└── README.md           # Project documentation

---

📖 How It Works

The calculator processes a list of sample annual incomes and generates:

1. Detailed Tax Reports — Per-taxpayer breakdown of income, tax, effective rate, and take-home pay.
2. Top Taxpayers — All taxpayers ranked by tax contribution.
3. High Earners List — Taxpayers falling in the highest tax bracket.
4. Summary Statistics — Aggregated figures across all taxpayers.

Sample Output

============================================================
SRI LANKAN TAX CALCULATOR (April 2025 Tax Reforms)
============================================================

============================================================
DETAILED TAX REPORTS
============================================================

Annual Income: Rs. 2,500,000.00
  Income Tax: Rs. 42,000.00 (1.68%)
  Take-Home (Annual): Rs. 2,458,000.00
  Take-Home (Monthly): Rs. 204,833.33
------------------------------------------------------------
...

---

🧠 Concepts Demonstrated

Concept	Usage
Functions	Modular tax calculation, reporting, and formatting
Lambda Functions	Inline filtering for high earners, sorting by tax paid
map()	Applying tax and take-home calculations across incomes
filter()	Extracting high earners from the income list
zip()	Pairing incomes with their computed taxes
sorted()	Ranking taxpayers by tax contribution

---

👤 Author

Sandeesh Fernando

---

📄 License

This project is open source and available for educational use.