CoinMarketCap Capital Gains CLI

This tool reads a CoinMarketCap transactions CSV and calculates FIFO cost basis, capital gain/loss, and holding days.

What It Does

• Parses portfolio transaction CSV exports.
• Matches sells to prior buys using FIFO lots.
• Calculates:
  • cost to buy
  • total sold for
  • capital gain/loss
  • days held
• Writes a report.csv file you can use in spreadsheets.

Install

npm install

Usage

npm start -- <path-to-transactions.csv> [output-report-path]

Examples:

npm start -- /Users/you/Desktop/Main_for_all/Main_transactions.csv
npm start -- /Users/you/Desktop/Main_for_all/Main_transactions.csv /Users/you/Desktop/report.csv

If output-report-path is not provided, output defaults to ./report.csv.

Notes

• The app validates that every sell can be matched to prior buys. If a sell exceeds available inventory, it throws an explicit error instead of silently dropping unmatched amounts.
• Some exports can include rounding drift. If this happens, inspect the flagged transaction in your source CSV and adjust data before rerunning.

Test

npm test

Quality Checks

npm run lint
npm run format:check