How to Comply with B2B E‑invoicing in Greece 2026: Step‑by‑step Compliance Guide

Understanding how to comply with B2B e‑invoicing in Greece 2026 is now a front‑burner priority for every company that issues tax documents to other businesses operating in the country. Greece’s Independent Authority for Public Revenue (AADE) is rolling out mandatory structured e‑invoicing in phases during 2026, building on the myDATA digital bookkeeping platform that has been operational since 2020 and the B2G e‑invoicing obligations already in force. The mandate requires affected taxpayers to issue, transmit, validate and archive invoices electronically through approved channels, either AADE’s own infrastructure, a direct API connection, or a certified PEPPOL Access Point.

This guide sets out the eligibility rules, the step‑by‑step procedure for registration and technical integration, the documents you need, the phased timeline, indicative costs, and the penalties for non‑compliance, giving CFOs, finance managers, accountants and general counsel a single, actionable reference.

Overview of the E‑Invoicing Process and Who It Applies To

A B2B e‑invoice, for the purposes of the Greek mandate, is a structured electronic document that is created in a prescribed format, transmitted through an approved channel, validated by AADE’s systems, and stored in a compliant digital archive. A PDF attached to an email does not qualify. The mandate covers sales invoices, credit notes and certain self‑billing documents issued between taxable persons established or VAT‑registered in Greece.

Compliance means satisfying four distinct obligations simultaneously. First, the invoice must be issued in the correct structured format, aligned with the European standard EN 16931 and, where PEPPOL is used, the PEPPOL BIS Billing 3. 0 specification. Second, the invoice must be transmitted to the buyer through one of the channels recognised by AADE: the AADE free invoicing application (aimed at micro‑enterprises), a direct API connection to the myDATA platform, or a certified PEPPOL Access Point operated by a licensed provider. Third, the invoice data must be reported to myDATA in real time or near‑real time so that AADE can cross‑check it against the buyer’s records and VAT returns.

Fourth, both the issuer and recipient must archive the e‑invoice for the retention period required under Greek tax law.

Every company within scope must therefore make three immediate decisions: which transmission channel to use, which technology provider (if any) to engage, and how to adapt internal ERP and accounting workflows. The sections below walk through each of those decisions in sequence.

Eligibility and B2B E‑Invoicing Requirements

Greece is phasing in the B2B e‑invoicing mandate by taxpayer size, measured primarily by annual gross revenue as reported to AADE. The phased approach follows the model already used for myDATA reporting obligations, which were themselves extended in stages between 2021 and 2024.

Who Is In Scope

The obligation applies to all taxable persons issuing invoices under the Greek Code of Tax Procedure and the Greek VAT Code (Law 2859/2000) for supplies of goods or services where both parties are identified by a Greek AFM (Tax Identification Number). Intra‑EU B2B supplies where the supplier is established in Greece are also expected to fall within scope once the EU’s VAT in the Digital Age (ViDA) regulation takes full effect, though the 2026 Greek mandate focuses on domestic and domestically reported transactions. Exports to third countries remain outside the structured e‑invoicing requirement, although myDATA reporting of export invoices continues to apply separately.

Phased Cohorts

Taxpayers should verify their cohort assignment directly on the AADE portal, as the authority publishes updated lists of obligated entities ahead of each phase. Certain categories of supply, including exempt financial services, insurance transactions and specific government‑to‑government transfers, may be excluded or subject to separate rules. Companies operating in regulated sectors should confirm any sector‑specific exemptions with their tax advisor or by reviewing the relevant ministerial decision published in the Government Gazette (FEK).

Step‑by‑Step Procedure for E‑Invoicing Compliance in Greece 2026

The following numbered procedure covers the core tasks every in‑scope company must complete. Each step identifies who is responsible and the typical time required.

Step 1, Establish Internal Readiness and Governance

1. Appoint a project lead. The CFO or General Counsel should designate a single point of accountability, typically someone in the finance or tax team, to coordinate between IT, procurement and external advisors.
2. Obtain board or management approval. Where company policy or articles of association require it, secure a corporate resolution authorising the e‑invoicing project, the budget and the engagement of external providers. This resolution also provides the legal basis for signing contracts with certified providers and granting any necessary powers of attorney.
3. Assess data protection impact. If invoices will contain personal data (for example, sole‑trader customer names and addresses), conduct or update a Data Protection Impact Assessment (DPIA) in line with GDPR requirements before sharing data with any third‑party provider.
4. Prepare a vendor procurement plan. Identify candidate certified providers or PEPPOL Access Points, request proposals, and set evaluation criteria covering SLA terms, liability allocation, data residency and pricing.

This governance phase typically takes 1–3 weeks and should not be treated as optional: the absence of a board resolution or a signed data processing agreement can create contractual and regulatory exposure later in the process.

Step 2, Register and Authenticate with AADE / myDATA

1. Log in to the AADE portal using the company’s TAXISnet credentials (linked to the entity’s AFM).
2. Select the e‑invoicing transmission mode. AADE currently offers three options: (a) the AADE free invoicing application, designed for micro‑enterprises with low invoice volumes; (b) a direct API connection from the company’s ERP to the myDATA platform; or (c) transmission via a certified third‑party provider or PEPPOL Access Point.
3. Generate API credentials or provider authorisation. For the direct API route, request production and sandbox API keys through the myDATA developer portal. For the provider route, the certified provider will handle authentication on the company’s behalf, the company must sign a written authorisation and, where required, a power of attorney.
4. Test in the AADE sandbox. Before going live, submit sample invoices in the test environment to confirm that credentials work, that invoice data is accepted, and that validation responses are correctly received and parsed by the company’s systems.

Registration and sandbox testing typically take 1–2 weeks, though companies choosing the direct API route should allow additional time for developer onboarding.

Step 3, Complete Technical Integration and Format Validation

1. Choose the invoice format. For PEPPOL transmission, the invoice must conform to PEPPOL BIS Billing 3.0, which implements the European semantic standard EN 16931. For direct myDATA API submission, invoices are transmitted as structured XML or JSON documents conforming to the myDATA schema published by AADE.
2. Map ERP fields to the required schema. Work with your IT team or ERP vendor to map each mandatory invoice field, supplier AFM, buyer AFM, invoice type code, line‑item descriptions, VAT rates, amounts and currency, to the corresponding element in the target schema. Document the mapping in a formal specification for audit purposes.
3. Implement the connector. Options include a native ERP module (available for major platforms such as SAP and Oracle), middleware from a certified provider, or a bespoke API integration. The choice depends on ERP complexity, invoice volume and budget.
4. Run validation tests. Submit a representative sample of invoice types (sales invoices, credit notes, self‑billed invoices) through the sandbox. Check that AADE returns a successful validation response, that the invoice UID (unique identification code) is generated, and that error codes are handled gracefully by the ERP.

Technical integration is the most variable phase, typically requiring 2–8 weeks depending on ERP complexity and whether the company uses a pre‑built connector or a custom build.

Step 4, Transmit, Archive and Reconcile

1. Go live with production invoices. Once sandbox testing is complete and all validation checks pass, switch to the production environment and begin transmitting live e‑invoices to buyers through the chosen channel.
2. Monitor AADE responses. Each transmitted invoice receives a validation response from myDATA. Establish an automated alert for rejected or errored transmissions so they can be corrected and re‑submitted promptly.
3. Archive e‑invoices. Greek tax law requires retention of accounting records, including invoices, for at least the period during which the tax authority may audit the relevant fiscal year. Industry observers expect most companies to retain e‑invoices for a minimum of ten years to cover extended audit and statute‑of‑limitation scenarios. Store invoices in their original structured format (XML/JSON), not solely as PDFs.
4. Reconcile with VAT returns. Cross‑check the myDATA summary of transmitted invoices against the company’s periodic VAT return before filing. Discrepancies between myDATA records and VAT declarations are a known trigger for AADE audit queries.

Go‑live itself takes approximately one week, but companies should plan for a 30–90 day monitoring period during which the finance team actively tracks validation rates and resolves any recurring errors.

Implementation Timeline Summary

Required Documents and Information for B2B E‑Invoicing

Before going live, companies should assemble the following documents. Missing any of these can delay registration, create contractual gaps with providers, or expose the company to regulatory challenge during an AADE audit.

E‑Invoicing Timeline Greece: Key Deadlines and Transition Windows

The e‑invoicing timeline in Greece has been adjusted several times since the mandate was first announced. AADE has used ministerial decisions published in the Government Gazette (FEK) to set and, where necessary, postpone go‑live dates for each cohort. The table below reflects the phased schedule as widely reported following the most recent AADE announcements. Companies should monitor the AADE website and the FEK for any further postponements or accelerations.

Early indications suggest that AADE intends to operate a soft‑landing period for each cohort during which administrative penalties may be reduced or waived for good‑faith compliance efforts. The duration and terms of any soft‑landing are set by ministerial decision and may differ between phases. Companies should not rely on the soft‑landing as a substitute for timely implementation, the likely practical effect is that only genuine technical difficulties, not delayed project starts, will attract leniency.

Costs, Fees and Tax Considerations

The costs of e‑invoicing compliance vary significantly depending on the company’s size, ERP platform, invoice volume and choice of transmission channel. The table below provides indicative ranges based on market conditions. All amounts are exclusive of VAT and should be verified with current provider quotations.

Expenditure on e‑invoicing integration is generally deductible as an ordinary business expense for Greek corporate income tax purposes. Companies should discuss the timing and classification of any capitalised software development costs with their tax advisor.

What Changes in 2026 for E‑Invoicing in Greece

Greece’s e‑invoicing landscape is not new, the myDATA platform has been collecting invoice summary data since 2020, and B2G e‑invoicing through the e‑PPS (National e‑Procurement System) has been mandatory for public‑sector suppliers since 2024. What changes in 2026 is the extension of the structured e‑invoicing obligation to B2B transactions, meaning that invoices exchanged between private‑sector entities must now be created, transmitted and validated electronically rather than simply reported to myDATA after the fact.

The key practical differences from the pre‑2026 regime are threefold. First, companies must issue invoices in a machine‑readable structured format (not PDF) and transmit them through an approved channel, this is a new obligation for B2B transactions. Second, AADE is aligning the domestic e‑invoicing infrastructure with the PEPPOL network and the European standard EN 16931, paving the way for interoperability with the EU’s forthcoming ViDA framework. Third, AADE has introduced updated API endpoints and sandbox environments for the 2026 mandate, requiring companies that previously integrated with myDATA for reporting purposes to update their technical connections.

Companies that were already reporting to myDATA will find the transition less disruptive, but they must still upgrade from summary reporting to full structured e‑invoice transmission.

Common Pitfalls and Penalties for E‑Invoice Non‑Compliance

• Late or missing registration. Companies that fail to register before their cohort’s go‑live date risk immediate enforcement action. Begin the registration process at least six weeks before the applicable deadline to allow for sandbox testing and error resolution.
• Incorrect field mapping. Mismatched VAT rate codes, missing buyer AFM fields or incorrect invoice‑type classifications are the most common causes of validation rejection. Run a full test cycle with every invoice type the company issues, sales invoices, credit notes and self‑billed documents, before going live.
• Inadequate provider SLA. If the certified provider’s system goes down and invoices cannot be transmitted, the issuing company, not the provider, bears the regulatory risk. Ensure the provider contract includes uptime guarantees, incident‑response times and clear liability allocation for transmission failures.
• Missing or non‑compliant archive. Storing invoices only as PDFs, or failing to retain the original structured file, can result in the invoice being treated as not validly issued. Implement archiving in the native XML or JSON format from day one.
• Failure to reconcile with VAT returns. Discrepancies between the invoices reported in myDATA and the figures declared in the periodic VAT return trigger automated AADE audit flags. Build a monthly reconciliation step into the finance team’s closing procedures.

Penalties and Appeal Procedure

AADE imposes administrative fines for failures relating to the issuance, transmission and archiving of tax documents, including e‑invoices. The penalties are set under the Greek Code of Tax Procedure (Law 4987/2022) and the relevant ministerial decisions. Fines may be imposed per invoice or as a lump sum per infringement type, depending on the nature of the violation. In addition to fines, non‑compliant invoices may be disallowed for VAT deduction purposes on the buyer’s side, creating knock‑on commercial disputes.

If a company receives a penalty notice, the immediate steps are: (a) gather all transmission logs, AADE validation responses and internal records for the relevant period; (b) review whether the infringement falls within the soft‑landing window, which may entitle the company to reduced or waived penalties; and (c) file an administrative appeal (endikofanís prosfygí) before the AADE Dispute Resolution Division within the deadline specified in the penalty notice, typically 30 days from notification. Engaging a lawyer experienced in Greek tax procedure at this stage is strongly advisable, as the appeal must set out the legal and factual grounds in a structured format and missed deadlines are not generally excusable.

Sources

1. AADE (Independent Authority for Public Revenue), Official Portal
2. AADE myDATA Platform
3. Greek Government (gov.gr), Official Announcements
4. Government Gazette (FEK), National Printing Office
5. OpenPEPPOL, PEPPOL BIS 3.0 and Access Point Information
6. European Commission, eInvoicing and VAT Digitalisation
7. Hellenic Ministry of Finance