What is a UBL invoice?
A UBL invoice is an invoice as structured XML data rather than an image or PDF. Accounting software reads it automatically: no retyping, no errors. It is the format behind Peppol BIS 3.0 and the Belgian B2B mandate.
What exactly is UBL?
UBL stands for Universal Business Language: an open XML standard from OASIS, also published as ISO/IEC 19845, for structured business documents such as invoices, credit notes and orders. A UBL invoice is not a picture of an invoice but machine-readable data: seller, buyer, invoice lines, VAT breakdown and payment information each live in their own field.
Because every field has a fixed meaning, any accounting package knows exactly where to find the total amount, the VAT number or the due date. That makes a UBL invoice a document systems can exchange directly with each other. It is precisely what "structured e-invoice" means in the legislation.
Why a PDF is not an e-invoice
A PDF is an image of an invoice, not data. A human has to read and retype it, or OCR software has to try to recognise it, with all the errors and manual work that entails. A UBL invoice, by contrast, flows straight into your accounting software: no retyping, no misread amounts, no invoices lost in a mailbox.
Since 1 January 2026 this also matters legally: under the Belgian B2B mandate, a structured e-invoice is required between Belgian VAT-registered businesses. A PDF by e-mail no longer legally counts as an e-invoice.
UBL, EN 16931 and Peppol BIS 3.0: how do they relate?
The three terms often appear together, and each describes a different layer of the same e-invoice. In short: UBL is the syntax (the file format), EN 16931 is the semantic model (what it must contain) and Peppol BIS 3.0 is the profile that combines both.
1UBL· The syntax
The XML format the invoice data is written in. UBL defines the fields and structure of the file itself.
2EN 16931· The semantic model
The European standard (from directive 2014/55/EU) defining what a core e-invoice must contain, independent of any file format.
3Peppol BIS Billing 3.0· The profile
Peppol's implementation profile that binds the EN 16931 model to UBL syntax and adds validation rules. It is the common language of the Peppol network.
Hybrid formats exist elsewhere: Factur-X in France and ZUGFeRD in Germany combine a PDF with embedded XML. The Peppol network, however, standardises on BIS 3.0 UBL.
Do you need to write UBL yourself?
No, and that is the good news. You never have to write or validate XML yourself. SendPol automatically generates a correct Peppol BIS 3.0 UBL invoice from your webshop orders, validates it and delivers it to your customer through a certified Access Point.
Credit notes are supported too: on a refund, a UBL CreditNote is created automatically and sent over the same network. Your invoicing stays consistent without you ever having to open an XML file.
Frequently asked questions about UBL
Is a PDF an e-invoice?
No. A PDF is an image that a human or OCR software has to read. An e-invoice is structured data (such as UBL) that accounting software processes automatically. Under the Belgian B2B mandate, a PDF by e-mail no longer legally counts as an e-invoice since 1 January 2026.
Can I open and read a UBL file?
Yes. A UBL invoice is an XML text file you can open in any text editor or browser. It is just not meant to be read by people: your accounting software imports it automatically and displays the invoice neatly formatted.
Does my customer need the same software as me?
No, that is exactly the point of the standard. Because UBL and Peppol BIS 3.0 are open standards, any accounting package connected to Peppol can process your invoice, regardless of which software you use to send it.
How do I create a UBL invoice from my webshop?
With SendPol it happens automatically: the plugin recognises business orders, generates a validated Peppol BIS 3.0 UBL invoice and delivers it through a certified Access Point. You never have to write or upload XML yourself.
Send UBL invoices without ever writing one
SendPol automatically turns your webshop orders into validated Peppol BIS 3.0 UBL invoices and delivers them through a certified Access Point.