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Rechnungs-Assistent vs KsefInvoice: catalog facts
Rechnungs-Assistent	KsefInvoice
Free Free and open source under the GPL-3.0-or-later license.	Free Freeware with no subscription or per-document KSeF fees.
Linux	Windows, Linux
Stores customer and item details for reuse Imports and exports data as CSV	Sends and retrieves documents through KSeF Handles invoices, corrections, receipts and multiple currencies
Designed for German invoicing Available for Linux	Interface is currently available only in Polish Focused on Polish tax and e-invoicing systems
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-3.0-or-later	License: Freeware
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 8, 2026	Official website Full listing and sources Checked October 8, 2026

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