XML_PROCESSING_INSTRUCTION: XML processing instruction (e.g

StandardKSeF FA(3), Polish national e-invoicing systemSeverityError: the invoice is rejectedSyntaxFA(3) XMLApplies toStructured invoices (FA(3) schema) submitted to the Polish KSeF. XSD codes come from the schema, semantic codes from the Ministry of Finance information sheet; KSeF rejects invoices that fail an error-level rule.

Official rule text

[XML_PROCESSING_INSTRUCTION] XML processing instruction (e.g. xml-stylesheet); KSeF rejects such invoices from 2026-10-19 (KSeF API 2.4.0, Weryfikacja faktury)

Why this error occurs

KSeF checks the FA(3) XML in two stages: XSD schema (structure, element order, data types, patterns such as NIP or dates) and semantic rules from the Ministry of Finance information sheet (consistency of amounts, annotations P_16 to P_23, roles of Podmiot2/Podmiot3, bank account formats, currency rates).

How to fix it

Fix the element named in the message. For XSD errors compare the element order and value pattern with the FA(3) schema; for semantic errors apply the cause and fix hints listed on this page. Re-validate before submitting to KSeF: a rejected invoice has no KSeF number and is not issued.

What the validator checks

Check levelparse / ksef_strict_xml

Typical causes

An integrator adds <?xml-stylesheet ...?> to attach a visualisation
Another tool injects a custom processing instruction

Check your invoice

Drop your XML or PDF on the validator and every failed rule is linked to its page here. Free, no account, the file is not stored.

Check your invoice →

Same check via API:

curl -F file=@invoice.xml https://einvoicechecker.com/v1/validate

Related rules

XML_BOM_PRESENT File starts with a UTF-8 BOM
XML_DISCOURAGED_CHARACTER Character discouraged by the W3C XML spec ([#x7F-#x84], [#x86-#x9F], [#xFDD0-#xFDEF],…
XML_DISCOURAGED_CHARACTER_MORE Summary
XML_ENCODING_NOT_UTF8 XML declaration names an encoding other than UTF-8
XML_PROCESSING_INSTRUCTION_MORE Summary

Frequently asked questions

What does XML_PROCESSING_INSTRUCTION mean?

XML_PROCESSING_INSTRUCTION is a ksef fa(3) rule: XML processing instruction (e.g. xml-stylesheet); KSeF rejects such invoices from 2026-10-19 (KSeF API 2.4.0, Weryfikacja faktury)

Will my invoice be rejected because of XML_PROCESSING_INSTRUCTION?

Yes. XML_PROCESSING_INSTRUCTION is flagged "fatal"; validators (KoSIT, Peppol access points, the German ZRE/OZG-RE portals, KSeF) reject the invoice until it is fixed.

Which formats does XML_PROCESSING_INSTRUCTION apply to?

Structured invoices (FA(3) schema) submitted to the Polish KSeF. XSD codes come from the schema, semantic codes from the Ministry of Finance information sheet; KSeF rejects invoices that fail an error-level rule. Syntax: FA3.

Source: KSeF FA(3) schema 1-0E + semantic rules (@ksefuj/validator 0.4). Catalogue generated from the official rule sets on 2026-10-15.