Preparing for EU e-invoicing 2027: Complete guide

E-invoicing is not just another bureaucratic formality. It is the biggest change in how companies issue and process invoices in the past twenty years. Yet most businesses are still waiting and hoping the deadline will slip. It will not. EU Council Directive 2014/55/EU and its national implementations set a clear timeline. Companies that start preparing at the last minute will repeat the same scenario as past e-receipt rollouts — stress, downtime, and unnecessary fines.

This article gives you the complete picture: what is changing, why, the key dates, and — most importantly — how to prepare for the transition step by step.

What changes and why

The European Union has been systematically pushing tax-administration digitalisation for years. The ViDA (VAT in the Digital Age) initiative, approved in late 2024, requires member states to introduce mandatory e-invoicing systems no later than 2028. Slovakia decided to implement it earlier — effective 1 January 2027 for B2B transactions.

The key difference from today: e-invoicing does not mean a PDF sent by email. An electronic invoice in legal terms is a structured data file(typically UBL 2.1 or UN/CEFACT CII format) transmitted through a central tax authority platform. Every invoice receives a unique identifier and is automatically validated against VAT registers. The system is modelled on the Italian SDI platform with local adjustments.

What this means in practice

• Invoices will not be sent directly to the buyer but via the tax authority platform
• The format must be machine-readable — PDF, Word, or scans will not be accepted
• The tax administration will have real-time access to invoice data
• Archiving must meet legal requirements of at least 10 years

Timeline: key milestones

The Ministry of Finance has published an implementation schedule in several phases. For companies the important thing is not to focus only on the final deadline but to use each phase to prepare.

1. 2026 Q3: Voluntary registration and testing

   The tax authority will open a sandbox environment for sending and receiving e-invoices. Companies can voluntarily register, test their systems, and tune integrations without sanction risk. This is the ideal time to identify technical problems.

2. 2026 Q4: Pilot operation for large companies

   Companies with annual revenue above €50 million will be included in a pilot programme. Pilot results will help fine-tune the system before nationwide launch. For smaller companies it is a signal: when the big players move, your buyers and suppliers will soon require compatibility.

3. 2027 Q1: Mandatory e-invoice for B2B

   All VAT payers will be required to issue and receive invoices exclusively in electronic structured format through the tax authority platform. Paper and PDF invoices will no longer be accepted for VAT purposes.

4. 2027 Q2: Extension to B2G transactions

   Mandatory e-invoicing will extend to transactions between businesses and the public sector (B2G). For companies trading with the state, local authorities, or state enterprises, this means another layer of compliance requirements.

5. 2028: Full integration with tax systems

   The e-invoice system will be fully integrated with VAT control statements and summary statements. Pre-filled tax returns based on e-invoices will become standard, significantly reducing administrative burden — but only for companies whose data is in order.

Technical requirements

The transition to e-invoicing is not just an organisational change — it requires concrete technical adjustments to your systems. The tax authority has published a technical specification defining three key areas.

Structured data formats

Invoices must be generated in structured XML format compatible with the European standard EN 16931. Two formats will be accepted: UBL 2.1 (used in most EU countries) and UN/CEFACT CII. Your invoicing software must be able to generate and process these formats.

API integration with the tax authority

Sending and receiving invoices will run through the tax authority's REST API. The system requires authentication through a qualified electronic signature (QES) or authorization token issued by the authority. Every submitted invoice goes through automatic validation — VAT ID checks, mandatory fields, and format correctness. Invalid invoices will be rejected with an error code.

Archiving and audit trail

The law requires electronic invoices to be retained in their original format for at least 10 years. Storing a PDF visualisation is not enough — you must archive the original XML file including the electronic signature and timestamps. The archive must be accessible to tax inspection in real time.

5 preparation steps for your company

The transition to e-invoicing does not have to be painful if you break it down into manageable steps. Start now and you will be ready by January 2027 — or find out how we can help via our digital accounting and e-invoicing readiness service.

1. Audit of the current invoicing process

   Map how you currently issue, receive, approve, and archive invoices. How many invoices do you process monthly? How many are paper? What software do you use? Where are the biggest bottlenecks? This audit shows how much work lies ahead and where the biggest risks are.

2. Select and implement compatible software

   Check whether your current accounting and invoicing system supports UBL 2.1 or CII formats and API connection to the tax authority platform. If not, start selecting a new solution. Regional systems like Pohoda, Money S3, and SuperFaktura have already announced e-invoice support — but confirm the upgrade will be available on time.

3. Automate payment matching via API

   E-invoicing brings a huge opportunity for automation. Connect the invoicing system to the banking API (PSD2) and automate the matching of incoming payments to issued invoices. This eliminates manual work and speeds up cash flow reporting.

4. Staff training

   Technology is only half of success. Your accountants, invoicing clerks, and managers must understand the new process. Plan training for Q4 2026 when the test environment is available, and give the team enough time to adapt.

5. Test run before go-live

   Use the tax authority sandbox (available from Q3 2026) to send test invoices, verify the integration, and simulate real operations. Identify problems in the test environment, not in production with real business partners.

Electronic invoicing is not just a compliance obligation — it is an opportunity for fundamental digital transformation of financial processes, saving companies an average of 60 % of invoice processing costs.