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Billy vs Invoice Ninja: catalog facts
Billy	Invoice Ninja
Paid Sold through the Mac App Store and the developer's site; the homepage does not state a…	Freemium Free plan available, with paid plans that carry a 30-day money-back guarantee.
macOS	Linux, Web
EN 16931 and XRechnung compliant e-invoices Data saved in open JSON files	Supports many payment gateways for one-click client payments Recurring invoices and auto-billing
macOS only Focused on invoicing rather than full accounting	Hosted service requires an account Some features are reserved for paid plans
Downloadable app	Downloadable app, Hosted service
Closed source	Open source
License not stated	License: AAL
Not stated if an account is needed	Account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 1, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.