Invoice CSV tool

A command-line tool that totals an invoice export per client, month and currency, and rejects bad rows with a clear reason.

Standard

The request

An internal command-line tool for an accountant on Windows and macOS: read a CSV export of invoices, print net, VAT and gross totals per client, per month and per currency, reject malformed rows with the row number and the reason, and optionally write the summary as CSV. Added later as a change request: a filter by month.

What was delivered

An installable Python command with a README for Windows and macOS
Comma or semicolon files, UTF-8 or Windows-1250, decimal point or decimal comma
VAT rounded per invoice, separate totals per currency, duplicate invoices reported
A CSV summary, a strict mode, and the month filter added as a change request

How it was checked

Tests: 271 automated tests pass on the delivered code (we reran them). One packaging test installs the tool into a fresh environment and could not run in our check environment.
QA: Every acceptance criterion passed, checked end to end with the real command, including a 200,000-row file and 30 randomized cases.
Security: 38 attack tests per stage. 9 security findings, 3 of them critical, all fixed.
Defects: 23 defects found by review, QA and security, 5 of them critical. 21 fixed; 2 minor gaps in test coverage are documented.
Load: Not applicable: a command-line tool, not a network service.