All You Need to Know About e-Invoicing, UBL XML and Peppol
Tools
• UBL • PEPPOL • XML • ISO19845 • E-INVOICE • BANKING •
Electronic invoicing is rapidly becoming the standard across Europe and beyond. Governments, enterprises, and SMEs are all moving away from PDFs and paper toward structured electronic invoices that can be processed automatically by software.
In this article, we explain:
- What e-invoicing really means
- What UBL XML invoices are and how they work
- What Peppol is and why it matters
- How these standards fit together
- How you can view, validate, batch-review, and even edit Peppol invoices without an ERP system, free of charge, online, without subscription or accounting software.
In 2026 electronic invoicing has crossed a tipping point. What was once a niche concern for governments and large corporations is now becoming standard practice for businesses of all sizes across EU, and increasingly beyond. Paper invoices and emailed PDFs are being phased out in favour of structured electronic invoices that can be processed automatically by software, with far-reaching consequences for accounting, compliance, and day-to-day business operations.
Access https://kibervarnost.si/peppol-editor/ to create a new Peppol invoice from an existing e-invoice
Access https://kibervarnost.si/peppol-viewer/ to batch review Peppol invoices
Access https://kibervarnost.si/ubl-viewer/ to batch review UBL invoices
What Is e-Invoicing?
The terminology can be confusing. Terms such as e-invoicing, UBL XML and Peppol are often used interchangeably, even though they refer to different layers of the same system. Understanding how they fit together is becoming essential not just for accountants and IT departments, but also for business owners, auditors, and consultants who deal with invoices every day.
At its core, e-invoicing means far more than sending a digital document. A true electronic invoice is a structured data file designed to be read directly by accounting or ERP systems. A PDF attached to an email may look digital, but it still requires manual handling and does not qualify as an e-invoice under most regulatory definitions. Structured invoices, by contrast, allow software to automatically extract supplier details, line items, tax information and totals without human intervention. The result is faster processing, fewer errors, better audit trails and, in many cases, quicker payment.
The most widely used format for structured invoices in Europe is UBL, short for Universal Business Language. UBL is an XML-based standard that defines exactly how invoice data should be organised. Instead of free-form text, every element of a UBL invoice, addresses, items, quantities, VAT rates, totals, and payment instructions, has a defined place and meaning. Because this structure is standardised, different software systems can exchange invoices without custom integrations or manual mapping.
An electronic invoice (e-invoice) is not just a digital document, it is a structured data file designed for automated processing by accounting and ERP systems.
A PDF sent by email does not qualify as an e-invoice.
True e-invoices:
- Contain machine-readable structured data
- Can be imported directly into accounting software
- Eliminate manual data entry
- Reduce errors and processing time
Benefits of e-Invoicing
- Faster billing and payments
- Fewer human errors
- Better auditability
- Lower administrative costs
- Improved compliance with national and EU regulations
What Is UBL XML?
UBL’s importance lies in its neutrality and reach. It is supported by accounting systems across Europe and underpins many national e-invoicing initiatives. Most notably, it forms the technical foundation of Peppol invoices. When businesses exchange invoices through Peppol, they are typically sending UBL XML documents that comply with additional, network-specific rules.
UBL is not just an industry convention; it is backed by formal international standardisation. ISO/IEC 19845:2015 defines the OASIS Universal Business Language as a generic XML interchange format for business documents. The standard provides a library of reusable data components, such as Address, Item and Payment, that are combined into complete document types like Invoice, Order and Despatch Advice. This modular design makes UBL both extensible and industry-agnostic, allowing countries, sectors and networks such as Peppol to impose extra requirements while preserving interoperability across borders and systems.
If UBL defines the language of electronic invoices, Peppol defines how those invoices are delivered. Peppol, which stands for Pan-European Public Procurement Online, is not a file format but a secure, standardised network for exchanging electronic business documents. It ensures that invoices are sent to the correct legal entity, arrive safely, and can be processed regardless of the software used by sender or recipient. Each participant in the network is identified by a unique Peppol Endpoint ID, and documents are routed automatically via certified access points according to common technical and legal rules known as Peppol BIS specifications.
UBL (Universal Business Language) is an XML-based standard for electronic business documents, including invoices, credit notes, and orders.
In simple terms:
UBL defines how invoice data is structured.
A UBL invoice contains clearly defined XML elements such as:
- Supplier and customer identifiers
- Invoice number and dates
- Line items
- VAT breakdowns
- Totals
- Payment details (IBAN, BIC)
- Buyer references and Peppol Endpoint IDs
Because the structure is standardized, software can read and validate invoices automatically, without guessing or manual mapping.
Why UBL Matters
The reliability of the UBL model is one of the reasons Peppol adoption is accelerating across the European Union. Belgium has already made Peppol mandatory for public procurement, and from 1 January 2026 all VAT-registered businesses will be required to exchange B2B invoices electronically, with PDFs and paper invoices no longer accepted. Similar trends are visible elsewhere. In the Netherlands, e-invoicing is mandatory for business-to-government transactions, and Dutch suppliers invoicing Belgian customers increasingly have no choice but to support Peppol. The direction of travel is unmistakable: structured e-invoicing via standardised networks is becoming the default.
- UBL enables straight-through processing
- Prevents retyping and mismatches
- Is widely supported across Europe
- Forms the basis for Peppol e-invoicing
Most Peppol invoices are, under the hood, UBL XML documents that follow additional business rules.
What Is Peppol?
Peppol stands for Pan-European Public Procurement Online. It is not a file format, but a secure, standardized network for exchanging electronic documents.
Think of it this way:
- UBL = the language
- Peppol = the delivery network
Peppol ensures that structured invoices are:
- Sent to the correct legal entity
- Delivered securely
- Interoperable across countries and software systems
How Peppol Works in Simple Terms
- Each participant has a Peppol Endpoint ID
- Documents are sent via certified Peppol Access Points
- Routing is automatic and standardized
- Invoices follow Peppol BIS specifications (business rules on top of UBL)
This prevents common problems such as: sending invoices to the wrong recipient, format incompatibilities, and lost or rejected invoices.
Legal Context: Why Peppol Is Becoming Mandatory
Across the EU, Peppol adoption is accelerating.
Belgium
- Since 2022: Mandatory for public procurement (B2G)
- From 1 January 2026: Mandatory for all B2B VAT-registered companies
- PDFs and paper invoices will no longer be accepted
- Significant fines apply for non-compliance
Netherlands and Beyond
- Mandatory for B2G transactions
- Rapid voluntary adoption in B2B
- Dutch suppliers invoicing Belgian companies must support Peppol
The direction is clear: structured e-invoicing via Peppol is becoming the default in EU
Peppol vs UBL: What’s the Difference?
| Aspect | UBL | Peppol |
|---|---|---|
| Role | Data format | Delivery network |
| Technology | XML schema | Secure transport infrastructure |
| Purpose | Structure invoice content | Send invoices reliably |
| Relationship | Used inside Peppol | Uses UBL (and CII) formats |
They are complementary, not competing technologies.
The Problem: “I Have an XML Invoice, Now What?”
In reality, many professionals encounter a practical problem with Peppol invoices. Raw XML e-invoices arrive without any accompanying software to read them. This is common during audits, month-end reviews, compliance checks or supplier disputes, especially when invoices are exchanged across borders. Opening a UBL or Peppol XML file in a text editor is technically possible, but rarely useful.
Free, Privacy-First Online Tools for UBL & Peppol
To solve this problem, we provide free, compliant, and browser-based tools for fast inspection, validation, and editing of electronic invoices.
Our browser-based tools have been developed to make structured invoices readable without requiring an ERP system, an account or a Peppol access point. A batch UBL viewer allows users to open one or multiple UBL or CII XML invoices directly in the browser and see a clear breakdown of suppliers, customers, line items, VAT, totals and payment details, with the option to export summaries to text or CSV. A dedicated Peppol viewer adds support for Peppol-specific fields such as Endpoint IDs and buyer references, suitable for compliance and cross-border reviews. For more advanced use cases, an online Peppol editor makes it possible to modify an existing Peppol invoice and re-export it as a new, valid XML document, which can be useful for corrections of an existing invoice or creating a new e-invoice.
1. Batch UBL Viewer
View and audit one or multiple UBL XML invoices at once
- Supports UBL and CII XML
- Displays:
- Supplier & customer data
- Line items
- VAT breakdowns
- Totals
- Payment details (IBAN/BIC)
- Batch summary with combined totals
- Export to TXT or CSV
- 100% client-side (JavaScript only)
- No uploads, no tracking, no accounts or registration.
2. Batch Peppol Viewer
Inspect Peppol BIS invoices without ERP access
- Reads Peppol-specific fields:
- Endpoint IDs
- Buyer references
- Legal entity identifiers
- Ideal for:
- Compliance checks
- Supplier verification
- Cross-border invoicing reviews
- Free, works entirely in browser, no uploads on server or subscriptions.
3. Peppol Editor
Edit an existing Peppol invoice and generate a new valid XML
- Modify invoice data safely
- Re-export as a compliant Peppol XML
- Useful for:
- Corrections
- Testing
- Training
- Regenerating invoices from samples
- No server processing and no data retention
- Completely free and always will be, no monthly subscription nor registration.
4. Peppol Invoice Forensic Auditor (Peppol Diff)
This tools allows to compare Peppol XML files and verify invoice data integrity. The Peppol Forensic Auditor is a specialized tool designed to ensure transparency and prevent fraud in electronic invoicing. It allows a side-by-side comparison of two Peppol invoices, clearly highlighting added, removed, or modified elements. This helps detect unintended or fraudulent changes, verify ERP exports, and confirm data consistency. All processing occurs locally in your browser using client-side JavaScript—no financial data or digital fingerprints are uploaded, and the tool is completely free with no registration required.
Simply select the Original XML and the Processed (or Suspicious) XML. The tool generates SHA-256 fingerprints to verify identity and integrity, summarizes key Business Metrics such as totals, taxes, and line counts, and provides Technical Forensics—including Footprint Delta and Tag Integrity—to detect changes in auxiliary data. A Detailed Audit Trail shows every path-level modification, making it invaluable for auditors, accountants, compliance officers, and internal control teams working with Peppol e-invoices.
5. Batch PDF E-Invoice Viewer, Extractor & Validator (Peppol, ZUGFeRD, Factur-X, EN16931)
Viewing and validating e-invoices in PDF format can be surprisingly tricky. Many “PDF invoices” are hybrid PDFs: documents that look like a normal PDF but actually contain an embedded XML file holding the true structured invoice data. While the PDF may look legitimate, the underlying XML can be outdated, incorrect, or even fraudulently modified, posing a risk to accounts payable, auditors, and finance teams.
Free, no registration tool Batch PDF E-Invoice Viewer & Validator solves this pain point. It allows you to securely inspect, extract, and validate the XML behind Peppol, ZUGFeRD, Factur-X, and EN16931-compliant PDFs. All fully client-side in your browser. No ERP required, no server uploads, no registration, and no data ever leaves your device.
Key features:
- Extract embedded XML from hybrid PDFs and display full invoice details.
- Support for Peppol BIS 3.0, UBL 2.1, CII, ZUGFeRD 2.x, Factur-X, and EN16931 profiles.
- Batch processing: view multiple invoices, summarize totals by currency, and export to TXT or CSV (for Excel).
- Validate required fields, line sums, VAT breakdowns, and compliance with EU invoice profiles.
- Inspect all critical data: invoice IDs, dates, parties (with Peppol IDs), line items, totals, allowances, charges, and payment info.
- Designed for accountants, auditors, finance teams, integrators, and SMEs needing a free, fast, and privacy-first tool to inspect, verify, and document electronic invoices.
In a VIF/VEC (fake invoice fraud attack), a perfectly formatted PDF may hide altered or fraudulent XML. By exposing and validating the underlying data, this tool ensures that what you approve or pay is exactly what the invoice intends to report. Simply select one or multiple PDF or XML invoices, extract the structured data, review, validate, and export for reporting or ERP ingestion—completely offline, completely safe.
Privacy First
All of these tools are designed with privacy in mind. Processing happens entirely on the user’s computer using JavaScript, with no uploads, no server-side storage and no tracking. For accountants, auditors and consultants handling sensitive financial data, this local-only approach is not just convenient but increasingly necessary.
Unlike many online converters:
- Invoices never leave your computer
- No servers, no uploads
- No analytics or tracking
- Designed for handling sensitive financial and GDPR data
- Aligned with strict EU privacy expectations
- Completely free and always will be
This makes the tools suitable for auditors, accountants, consultants, and security-conscious organizations. E-invoicing with UBL and Peppol is no longer optional, it is core business infrastructure.
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