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Free FA(3) validator for KSeF

Paste an FA(3) XML or an invoice JSON. We check it against the official Ministry of Finance XSD and explain every problem in plain language.

Your document is checked in memory and not stored. Sandbox only: nothing is sent to KSeF.

Want a heads-up when KSeF production opens?

Optional. Leave your email and we will write only about KSeF e-invoicing.

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