Short answer: use a form, not an XML editor

No, a small business does not need to write XML to send a Peppol invoice. A Peppol invoice is a structured data file that complies with Peppol BIS Billing 3.0 specification, that is, an invoice whose fields are machine-readable (the computer automatically understands them without the person having to manually transfer the data). You fill in the standard invoice form in your e-invoice or accounting software: customer name, amounts, VAT, payment term. The software creates an XML file from it itself and sends it via the Peppol network. On August 17, 2026, it became mandatory new BIS Billing 3.0 version, so it's worth checking that your operator is using the latest set of validation rules.

Your job is limited to entering the usual invoice data. If the customer or operator says that the invoice „did not pass validation“, this does not mean that you should manually correct the XML code. It means that some field is missing or incorrect in the software and you need to review it in the form.

What is Peppol and what is it not?

Peppol is a secure data exchange network through which structured invoices move from one system to another. Peppol itself is not software or a form that you fill out. It is like a postal service for invoices. The content that moves on this network must comply with Peppol BIS Billing 3.0 rules, which describe which data fields an invoice must contain and in what structure. The structure is called UBL (Universal Business Language) and is one of the most common XML-based invoice formats. XML (Extensible Markup Language) is simply a machine-readable file format that computers use to exchange data. It is usually not visible to humans at all.

A Peppol invoice is not the same as a PDF invoice sent by email, nor is submitting a VAT return to the tax authorities. These are three different obligations: sending the invoice to the customer, machine-readability of the data, and tax reporting to the state. These often go hand in hand, but do not have to.

What to check before creating an invoice?

Before you open an account, check these things:

  • Customer's Peppol readiness: Is the buyer able to receive Peppol invoices at all and what is their exact Peppol ID, or address, to which the invoice should be sent.
  • Buyer reference or order number: valid Peppol rules According to the law, the invoice must contain either a buyer reference or an order number. Without them, the invoice validation will fail.
  • Customer-specific instructions: A large client or public sector institution wants their exact internal code, not your made-up reference. Ask the client for this number directly, rather than guessing it yourself.

Create and receive a Peppol invoice in five steps

  1. Select customer and shipping method: mark in the software that the invoice will be sent via the Peppol channel, not by email.
  2. Add seller and buyer identifiers: Your and the customer's Peppol IDs are usually filled in automatically from the customer card.
  3. Enter invoice lines, VAT and payment terms: products or services, prices, VAT rate and payment term.
  4. Add buyer reference or order number: this field is not optional.
  5. Run validation and get: The software automatically checks the invoice before sending and notifies you if anything is missing.

Which fields are more important than they seem at first glance?

Imagine an invoice for 1,200 euros to a Latvian customer. The amount and VAT are correct, but the invoice may still bounce if:

  • the invoice number is not unique and repeats a previous invoice;
  • the currency code is incorrect or missing;
  • the VAT category and rate do not match (e.g. 0% VAT without justification);
  • the seller or buyer identifier is misspelled;
  • payment details, such as IBAN or reference number, are missing or incorrect;
  • The buyer reference or order number is empty.

It is the last point that is the most common mistake. Peppol rules This is a required field, and its absence is a fatal validation error, not a recommendation that can be ignored.

PDF, attachments and rejected invoices

The PDF invoice is human-readable, but it is not a Peppol invoice. Explanation from the Ministry of Finance According to the e-invoice, an e-invoice is a machine-readable file that does not require the recipient to manually enter data. An image or PDF does not meet this requirement. Many software programs include a PDF copy of the structured invoice so that a person can quickly review the invoice content, but this is an additional convenience, not a replacement.

If the invoice does not reach the customer, it is a delivery error, usually an incorrect Peppol ID or a connection problem. If the invoice reaches the customer but their system rejects it, it is a business error, usually due to a missing buyer reference or incorrect details. Check these two things first before doubting the reliability of the software.

What is in force in Estonia and Latvia now and what is coming?

In Estonia, an accounting entity that has registered itself as an e-invoice recipient in the e-business register can, starting from 2025, demand from the seller: e-invoice, unless the parties have agreed otherwise. Estonia allows the use of both the local and European, or Peppol, standards, and the ministry recommends the latter to entrepreneurs, as it is more widely used across the European Union.

In Latvia, the requirements are stricter and the timeline is clearer. From 1 January 2025, structured e-invoices will be mandatory for G2G, B2G and G2B transactions, and from 1 January 2026, invoice data for these same sectors will also have to be transmitted. Valsts iēmušenu dienesti (VID). In B2B transactions, submission of data to the VID is voluntary until December 31, 2027, but from January 1, 2028, submission of structured e-invoices and their data to the VID will become mandatory also in transactions between Latvian companies.

At the European Union level, the next important deadline is 1 July 2030, when ViDA reform e-invoices will become the default payment method in cross-border B2B transactions. If you start sending Peppol invoices today, you will be ready for this deadline years before it becomes a problem for anyone else.

FAQ

Does a small business need to write XML to send a Peppol invoice?

No, a small business does not need to write XML. You fill out a standard invoice form in your software and the software will create the XML file itself and send it via the Peppol network.

What is Peppol?

Peppol is a secure data exchange network for invoices. It is not software, but rather a postal service that delivers structured invoices.

What are the most common errors when sending a Peppol invoice?

The most common error is missing the buyer reference or order number. This is a required field and its absence will result in a validation error.

What is the difference between a Peppol invoice and a PDF invoice?

A PDF invoice is human-readable, but not machine-readable. A Peppol invoice is a structured XML file that computers can automatically process.