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Billy vs SolidInvoice: catalog facts
Billy	SolidInvoice
Paid Sold through the Mac App Store and the developer's site; the homepage does not state a…	Freemium Free to self-host; the hosted service is a monthly subscription with a 14-day trial.
macOS	Web, Self-hosted
EN 16931 and XRechnung compliant e-invoices Data saved in open JSON files	Quotes, recurring invoices and automatic reminders Online payments via Stripe and PayPal
macOS only Focused on invoicing rather than full accounting	Self-hosting requires a PHP server setup Focused on invoicing rather than full accounting
Downloadable app	Self-hosted, Hosted service
Closed source	Open source
License not stated	License: MIT
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 2, 2026

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