What Is E-Invoicing and How Does It Work? Complete Guide to Formats, Compliance, and Implementation

Key takeaways

• An e-invoice is a structured data file, not a picture of an invoice. A PDF is a digital invoice, but not an e-invoice.
• E-invoices move directly from the seller’s system to the buyer’s system, often through networks such as Peppol or through government platforms.
• The main standards are EN 16931 (the European semantic standard), UBL and UN/CEFACT CII (syntaxes), and Peppol (the exchange network and specifications).
• E-invoicing is mandatory in a growing number of countries. Requirements differ by market, and in the EU, e-invoicing becomes mandatory for intra-EU B2B transactions from July 1, 2030, under the ViDA package.
• For large organizations, the main benefits are lower processing costs at high volumes, fewer errors, faster payment cycles, and one consistent process across countries and entities.
• A single e-invoicing platform can connect several ERP systems to government platforms and the Peppol network, so companies don’t need a separate solution for each country.

What is e-invoicing?

E-invoicing (electronic invoicing) is the automated, end-to-end exchange of structured, machine-readable invoice data directly between the supplier’s and buyer’s billing or ERP systems without manual data entry. Under EU law (Directive 2014/55/EU), an e-invoice is one that has been issued, transmitted, and received in a structured format that allows automatic and electronic processing. This means an e-invoice is not a PDF, a scanned paper invoice, or an invoice image sent by email.

In an e-invoice, each piece of information – supplier name, VAT number, line items, quantities, amounts, tax rates, payment terms – sits in a defined field that software can read. Because of this, the buyer’s accounts payable (AP) or ERP system can import the invoice, validate it, and route it for approval without anyone retyping the data. A human-readable version of the invoice can be generated for viewing, but it is secondary: the legally relevant invoice is the structured data file.

What counts as an e-invoice:

• An XML file in a recognized format, such as UBL, UN/CEFACT CII, or a national format required by a tax authority
• An EDI message (for example, EDIFACT INVOIC) exchanged between trading partners
• A hybrid invoice (such as Factur-X or ZUGFeRD) that combines a PDF with embedded structured XML data, where the XML is the part that is processed

What does not count as an e-invoice:

• A PDF or Word invoice sent by email
• A scanned paper invoice or an image file (JPG, TIFF)
• An invoice displayed as unstructured HTML on a web page or in an email body
• A paper invoice sent by fax

How does e-invoicing differ from traditional and digital invoicing?

The terms are often used interchangeably, but they describe different things. Traditional invoicing means paper invoices printed, mailed, and keyed in by hand. Digital invoicing usually means an invoice in an electronic but unstructured form, most often a PDF sent by email. It removes paper, but someone still has to read it and enter the data. E-invoicing removes both paper and manual data entry because the invoice is data from the start.

How does e-invoicing work, step by step?

The end-to-end process looks broadly the same in most countries. What changes is the channel and whether a tax authority is involved in real time.

1. The supplier creates the invoice. The invoice is generated from data already in the supplier’s ERP or billing system, so nothing needs to be retyped.
2. The data is converted into the required format. The e-invoicing platform automatically maps ERP data to the format required by the buyer or the tax authority, such as UBL, CII, or a national XML schema.
3. The invoice is validated. Before sending, the platform automatically checks that the file is technically correct, that all mandatory fields are present, and that tax logic (VAT rates, totals, identifiers) is consistent. Many organizations also add their own business rules. If an error is found, the invoice is stopped and flagged for correction instead of being rejected by the recipient.
4. The invoice is transmitted. The platform sends the invoice through the right channel for each country and trading partner: a network such as Peppol, a direct EDI connection, a supplier portal, or a government platform. In “clearance” countries, the tax authority must approve the invoice before it is valid or delivered.
5. The buyer receives and imports the invoice. The buyer’s system automatically reads the data, checks it against purchase orders and goods receipts, and routes it for approval.
6. The invoice is approved and paid. Because matching and approval happen faster, payment can be scheduled on time, and statuses can flow back to the supplier.
7. Both parties archive the invoice. The e-invoice is stored electronically for the legally required retention period, with a full audit trail.

What are the main e-invoicing standards and formats?

Standards define what data an e-invoice contains and how it is written, so that different systems can understand each other. Below are the most popular e-invoice formats:

Standards also differ by region. Europe relies mainly on EN 16931, implemented in UBL or CII syntax and often exchanged via Peppol. Many countries in Latin America, the Middle East, and Asia use national XML formats defined by their tax authorities instead, while Peppol is also expanding in the Asia-Pacific region, for example, in Australia, New Zealand, Singapore, and Japan.

EN 16931 was originally designed with public procurement in mind. As more countries extended mandates to B2B transactions, the standard was revised, and an updated version was published in 2026.

In practice, companies don’t need to generate each of these formats in their ERP. An e-invoicing platform can take the ERP’s native output, such as an SAP IDoc file, and convert it into the format required by each country or trading partner.

How does Peppol enable cross-border e-invoicing?

Peppol works like a postal network for e-invoices. Each company connects once to a certified Peppol access point and can then exchange documents with any other participant on the network, regardless of which provider they use. Because the format and the delivery rules are shared, for example, a company in Belgium can send an invoice to a customer in Norway or Singapore without a separate technical connection for each partner. For a more detailed explanation, read what Peppol is and how it works.

What are the main e-invoicing models?

E-invoicing models describe how and when the tax authority is involved in the exchange of invoices between businesses. The model a country uses determines how companies must integrate their systems, when an invoice becomes legally valid, and what happens if a government platform is unavailable.

• Clearance models: Invoices must pass through a government platform, which validates and approves them before they become legally valid or reach the buyer. This model is common in Latin America and increasingly used in Europe and Asia.
• Post-audit models: Invoices are exchanged directly between businesses. The tax authority doesn’t see them in real time but can check them later, typically during an audit.
• Decentralized models: Businesses exchange invoices directly or through service providers, often over the Peppol network, where each participant connects through a certified access point. In the 5-corner variant, invoice data is also passed to the tax authority as the “fifth corner.” In some countries, such as France, Slovakia, and the UAE, using a certified provider is mandatory.

Companies operating in several countries often need to work with more than one model at the same time. Comarch E-Invoicing, for example, connects directly to clearance platforms such as KSeF in Poland and SdI in Italy, and as a certified Peppol Access Point, it also supports decentralized exchange, including in Slovakia and the UAE, where it is an accredited e-invoicing provider.

The shift from post-audit to real-time control is explained in more detail in this overview of how e-invoicing is changing global trade.

Is e-invoicing mandatory?

It depends on the country and the type of transaction. E-invoicing has moved from a voluntary efficiency measure to a legal requirement in many markets, mainly because structured invoice data helps tax authorities reduce VAT fraud and close the tax gap.

Mandates typically cover one or more of three areas:

• B2G (business-to-government): In the EU, public authorities have been required to accept e-invoices based on the EN 16931 standard. Many countries also require suppliers to send them.
• B2B (business-to-business): A growing number of countries require companies to issue and receive structured e-invoices for domestic transactions, often in phases starting with the largest taxpayers.
• E-reporting: Some countries require invoice or transaction data to be reported to the tax authority, sometimes in near real time.

Which countries require e-invoicing?

In the EU, B2B e-invoicing is already mandatory in several countries, including Italy (since 2019), Belgium and Croatia (since 2026), Poland (since 2026), and France (since September 2026). Others have set dates, such as Slovakia (2027), the Netherlands (2030), and Germany (receipt mandatory since January 2025, issuance phased in from 2027). At the EU level, the VAT in the Digital Age (ViDA) package – Council Directive (EU) 2025/516 – makes structured e-invoicing and digital reporting mandatory for intra-EU B2B transactions from July 1, 2030, and lets member states introduce domestic mandates without prior EU approval.

Outside the EU, e-invoicing mandates are just as widespread. Countries such as Mexico, Brazil, and Chile have used clearance models for many years, and mandates have also been introduced or announced across the Middle East and Asia, including Saudi Arabia, Malaysia, and the United Arab Emirates.

While compliance drives the adoption of e-invoicing, global organizations leverage mandates as an opportunity to modernize their Financial Supply Chain. With Comarch’s automated compliance updates, regulatory shifts become seamless background updates rather than complex IT projects.

Because formats, deadlines, thresholds, and channels differ from country to country, companies operating in several markets need to track each jurisdiction separately and plan for requirements that change over time. New mandates, postponements, and technical updates are published regularly in our e-invoicing legal updates section, which covers changes country by country.

What are the benefits of e-invoicing for large enterprises?

For organizations that process tens of thousands or millions of invoices a year, e-invoicing changes the economics and the structure of invoice processing, resulting in:

• Lower processing costs at scale. The cost of paper, printing, postage, manual data entry, and error correction grows with every invoice. With e-invoicing, most of the work is automated, so volume increases don’t require proportional increases in headcount. Read more about how e-invoicing compliance can become a source of operational savings.
• Fewer errors and disputes. Validation before sending catches missing fields, wrong tax rates, and incorrect totals, which reduces rejected invoices and supplier queries.
• Faster invoice cycles and better cash flow. Suppliers get paid on time more often, and buyers can take advantage of early-payment terms. For accounts receivable teams, faster delivery and status tracking shorten days sales outstanding (DSO).
• One process across countries and entities. Groups with many subsidiaries, shared service centers, or ERP instances can run a single, standardized invoice flow while still meeting local requirements in each country.
• Compliance by design. When invoices are created in the formats required by each market and sent through approved channels, compliance becomes part of the process rather than a separate project for every new mandate.
• Complete audit trail and easier audits. Every invoice has a time-stamped history, from creation to archiving, which simplifies internal controls and tax audits.
• Better visibility and data. Structured invoice data can feed reporting on spend, supplier performance, processing times, and error rates. See how reporting supports large-scale e-invoicing operations.
• Stronger fraud prevention. Verified sender identities, validation rules, and anomaly detection make invoice fraud and duplicate payments harder than with PDFs sent by email.

Smaller suppliers benefit too: they receive payments faster, face fewer disputes, and, in many cases, can send e-invoices through simple web portals without their own integration.

How do you implement e-invoicing in a company?

Implementing e-invoicing in a large organization is as much an organizational project as a technical one. Typical timelines range from several weeks for a single country and a limited set of flows to several months for multi-country rollouts with complex ERP environments.

1. Map your obligations: List the countries where you operate and the mandates that apply to you: B2G, B2B, e-reporting, archiving rules, and deadlines.
2. Inventory your invoice flows: Identify inbound (AP) and outbound (AR) flows, volumes per country, current channels, and the ERP systems and entities involved.
3. Decide how to integrate with your ERP: An e-invoicing solution should connect to your existing ERP environment rather than require you to replace it. If you use multiple ERP systems, choose a solution that supports them all, and ensure your e-invoicing setup isn’t tied to a single ERP provider in a way that would make switching difficult later. In practice, integration usually works in one of three ways: through a ready-made connector for the ERP or accounting software, through an API, or through file-based exchange (for example, XML or IDoc files) that the platform converts into the required formats. For example, Comarch e-Invoicing connects to SAP S/4HANA and SAP ERP through a dedicated SAP connector, and to systems such as Oracle Fusion and Microsoft Dynamics through an API or file-based exchange. For smaller companies with simpler flows, accounting software with built-in e-invoicing support may be enough.
4. Choose a deployment model: In a SaaS (cloud) model, the provider manages infrastructure, security, monitoring, and updates for legal changes, and costs are usually subscription-based and tied to document volumes. In an on-premise model, you keep full physical control of the data, but you carry the upfront investment and need internal IT resources to maintain the system and comply with regulatory changes.
5. Clean up master data and define validation rules: Most e-invoice rejections come from incomplete or inconsistent data at the source: supplier details, tax identifiers, units, and codes. Fixing this early saves time later.
6. Onboard your trading partners: Large partners typically connect via EDI or Peppol, while smaller suppliers may use a portal. Plan communication and support for each group.
7. Test, roll out in phases, and monitor: Start with the countries or flows with the nearest deadlines or the highest volumes, then extend. Monitor delivery statuses, rejections, and processing times.
8. Set up compliant archiving: Make sure both sent and received e-invoices are stored for the required retention period in each country, with a full audit trail.

See how the Comarch E-Invoicing platform can support this process across countries and ERP systems.