In addition to PDF invoices, you can also submit UBL files (XML e-invoices) by email to eConnect. A valid UBL invoice is processed directly without OCR recognition, which is faster and more reliable than PDF conversion. This article explains how this works and what happens if the XML is not valid.

When you submit a UBL invoice by email, the platform validates the file directly against the supported standards. The following UBL formats are recognised:

• SI-UBL 2.0 (NLCIUS, the Dutch standard)
• Peppol BIS Billing 3.0 (the European Peppol standard)

Is the XML valid? Then the invoice is immediately processed and delivered, without any OCR recognition being required. This means faster processing and higher reliability, because no interpretation of visual elements is needed.

If the XML file is not valid (for example due to missing mandatory fields or a deviating structure), the platform automatically switches to a fallback. How that fallback works depends on the situation:

• UBL with accompanying PDF: if a PDF invoice is also included in the email alongside the invalid XML, the PDF is processed via OCR recognition.
• UBL without PDF: if no PDF is included, the invoice cannot be processed and you will receive an error message.

Tip: want to check in advance whether your UBL file is valid? Use the eConnect Document Validator, a free online tool with which you can validate any UBL file.

ZUGFeRD (Germany) and Factur-X (France) are hybrid invoice formats: a PDF with an embedded XML in CII format. For these invoices the platform first attempts to extract and process the embedded XML.

If the embedded XML is not valid, the system falls back to OCR processing of the PDF component. A ZUGFeRD invoice that passes external validators but is still processed as a PDF by eConnect may indicate a difference in the validation rules for the embedded XML.

The platform can only save valid UBL invoices (Peppol BIS Billing 3.0 or NLCIUS). When a ZUGFeRD or Factur-X invoice is processed as a PDF via the IDR (because the embedded XML was not valid), the OCR output must still be transformed into valid UBL before the invoice can be saved. If that transformation fails — for example because the recognised data does not contain sufficient fields for a valid UBL invoice — then the invoice cannot be saved. The IDR recognition itself virtually never fails in practice; it is the subsequent transformation and validation step that can fail in rare cases.

The older SimpleInvoicing formats (SI 1.1 and SI 1.2) have not been permitted on the Peppol network since 2024. eConnect can in many cases still transform these formats into a valid NLCIUS invoice when submitted by email, provided all essential data is present. With missing data, validation may fail.

The recommendation is to switch to SI-UBL 2.0 (NLCIUS) or Peppol BIS Billing 3.0 for reliable processing.

eConnect has a feature that automatically repairs known errors in UBL files via an XSL transformation. Non-essential missing fields are supplemented with default values, so that the invoice can still be processed. This feature is continuously developed based on patterns found in practice.

It is useful to know the distinction between conversion and transformation:

• Conversion: a PDF invoice is converted to an e-invoice (XML). This requires OCR recognition and always involves an interpretation step.
• Transformation: an e-invoice in one XML format is converted to another XML format. This is more reliable because the source data is already structured.

eConnect supports automatic transformation between more than 20 XML standards, including sector-specific formats such as DICO, SETU, SEEF and XRechnung.

Would you prefer to receive invoices directly via Peppol instead of by email? That is possible if your organisation is registered on the Peppol network.