// the find
ept/invoicing
Ruby invoicing framework gem
An ActiveRecord-based invoicing framework for Rails apps, handling line items, tax rates, currency, and invoice rendering to HTML/UBL XML. It's for Rails shops needing custom invoicing logic rather than a hosted billing API, but it's effectively abandoned — the README itself points to code-mancers/invoicing as the maintained fork.
Supports UBL (Universal Business Language) XML export alongside HTML rendering, which is a real e-invoicing interchange format and not trivial to bolt on after the fact. The domain is cleanly decomposed into separate modules (tax_rate, currency_value, line_item, time_dependent, taxable) rather than one monolithic Invoice model, which is how invoicing logic should be structured. Test suite includes reference-output fixtures (ref-output/*.html, *.xml) that diff generated invoices against known-good output, catching rendering regressions.
Last pushed in 2015 and pins to ActiveRecord >= 2.1, tested only against AR 2.2.2 — this predates Rails 3 and won't run on any Rails app built in the last decade without a rewrite of the AR integration layer. The README's FEATURES section is literally just 'TODO', so you're reading source to find out what it does. Only MySQL and PostgreSQL are supported, no adapter abstraction for anything else. The author's own README tells you to use a different repo instead, which is as clear a signal as you'll get that this isn't worth adopting as-is.