Mandatory B2B E‑invoicing in Greece 2026, a Practical Compliance Guide for Businesses

Mandatory B2B e‑invoicing in Greece 2026 represents the most significant shift in Greek tax-administration infrastructure since the launch of the myDATA platform. Greece is rolling out compulsory structured electronic invoicing in phases throughout 2026, requiring every VAT-registered business to issue, transmit and receive invoices through AADE-approved digital channels. The reform aligns Greece with broader EU digital-tax initiatives and will affect ERP systems, supplier contracts, VAT reporting workflows and internal controls across virtually every sector. This guide provides CFOs, finance directors, general counsel and SME owners with the exact timelines, technical specifications and step-by-step actions needed to achieve full B2B e‑invoicing compliance before enforcement begins.

Executive Summary, What This Means for Your Business

Yes, B2B e‑invoicing is now mandatory in Greece. Large enterprises, those with gross revenues exceeding €1,000,000 in FY 2023, were required to begin issuing structured e‑invoices from early 2026, following a brief postponement of the original deadline. All remaining VAT-registered entities face a compliance deadline later in the year. Industry observers expect that AADE will enforce these obligations rigorously, leveraging the real-time data flows already established through the myDATA ecosystem.

• Who must comply. Every VAT-registered business operating in Greece, phased by annual revenue.
• When. Phase 1 (large businesses) commenced in early 2026; Phase 2 (SMEs and remaining entities) is set for 1 October 2026, subject to official confirmation.
• Top 3 actions now. (1) Confirm your phase and deadline, (2) audit your ERP and accounting-software readiness for structured e‑invoice output, and (3) notify suppliers and customers of your migration timeline.

1. Timeline and Who Is in Scope, E‑Invoicing Greece 2026 Dates and Phases

Greece is implementing mandatory B2B e‑invoicing in two main phases, following earlier B2G requirements that have been in force since 2025. The original Phase 1 start date was set for 2 February 2026 but was briefly postponed by AADE to allow additional technical preparation. The table below summarises the confirmed implementation milestones as reported by AADE, Deloitte Greece, EY Greece and KPMG.

Implementation Phases, Transitional Windows

AADE’s phased approach mirrors the strategy adopted by other EU member states. Phase 1 targets entities that already have mature accounting systems and the resources to integrate quickly. The brief postponement from the original 2 February 2026 date, as reported by KPMG, was intended to give technology providers additional time to finalise API connectivity with AADE’s production environment. Businesses in Phase 1 should treat the postponed date as firm and ensure all systems are operational.

Phase 2 entities, primarily SMEs, have until 1 October 2026 based on current advisory reporting from EY Greece and RSM Global. However, AADE has indicated that transitional provisions may apply to certain micro-enterprises and entities in remote regions. Businesses should monitor AADE’s official announcements for any further adjustments. Early indications suggest that no additional postponement is anticipated for Phase 2.

2. Legal and Regulatory Basis, What the Law Requires

The legal foundation for mandatory B2B e‑invoicing compliance in Greece rests on a series of ministerial decisions issued by AADE, building on the framework established by the myDATA digital platform. The European Commission’s Digital Building Blocks programme provides the overarching EU-level context, supporting Greece’s transition under the broader ViDA (VAT in the Digital Age) initiative.

Scope of the Obligation, B2B, B2G and Cross-Border

The obligation applies to all domestic B2B transactions between VAT-registered entities established in Greece. B2G e‑invoicing, already operational since September 2025 for transactions above the €2,500 threshold, continues under the existing myDATA rules and is not affected by the new B2B phases. Cross-border transactions with counterparties in other EU member states or third countries are not currently subject to the mandatory structured e‑invoicing requirement, although businesses must still report such transactions to myDATA using the existing summary-data transmission rules.

Certain narrow exemptions may apply to entities operating under simplified tax regimes or to specific categories of transactions (such as retail receipts issued to final consumers, which remain outside the B2B scope). Businesses should verify their exact obligations against the AADE’s published decision and, where necessary, seek professional advice to confirm whether any exemptions apply to their particular circumstances. Digital invoicing in Greece has rapidly moved from optional to compulsory, and the practical effect will be that paper and PDF invoices between businesses will no longer satisfy statutory requirements for in-scope transactions.

3. Technical Requirements and Formats, Mandatory B2B e‑Invoicing Greece 2026 Integration

Greece’s e‑invoice requirements centre on the transmission of structured invoice data to AADE’s myDATA platform in real time or near-real time. Unlike simple PDF or scanned-image invoices, a structured e‑invoice is a machine-readable data file that AADE can process, validate and cross-reference automatically against the recipient’s records.

Required Data Fields

The structured e‑invoice must contain a defined set of mandatory data fields aligned with AADE’s myDATA schema. The table below summarises the core data elements that every e‑invoice must include.

ERP Mapping and E‑Invoicing Integration Checklist

Achieving full e‑invoicing integration with your ERP system requires a structured approach. The following checklist is designed for finance and IT teams to work through together.

1. Confirm your ERP vendor’s myDATA API module is available and updated to the latest AADE schema version.
2. Map all internal invoice types to the corresponding myDATA invoice-type codes.
3. Configure automatic generation of structured XML output for every B2B invoice.
4. Establish a secure API connection to AADE’s myDATA production environment (not just the test environment).
5. Implement automated MARK retrieval, every issued invoice must receive and store the AADE-assigned MARK before being sent to the customer.
6. Set up error-handling workflows for rejected or failed transmissions (retry logic, alerts to finance team).
7. Run a parallel testing period, issue invoices in both the old format and the new structured format for at least 30 days before your mandatory start date.

Vendor, Peppol and Cross-EU Considerations

Businesses that operate across multiple EU jurisdictions may already use the Peppol network for B2G e‑invoicing. While Greece’s domestic B2B mandate operates primarily through AADE’s own myDATA infrastructure rather than Peppol, the likely practical effect is that interoperability between myDATA and Peppol will increase over time as the EU’s ViDA framework matures. For businesses with operations in Poland (which uses the KSeF system), industry observers note that lessons from the Polish rollout, particularly around API stability and the handling of credit notes, are directly relevant to the Greek implementation. Selecting an e‑invoicing integration ERP solution or middleware provider that supports both myDATA and Peppol will provide the greatest flexibility for cross-border operations.

For further context on structuring international commercial relationships, including invoice terms, see our dedicated guide.

4. Operational Implementation, People, Process and Systems

Moving from technical readiness to full operational compliance requires a coordinated effort across finance, IT, procurement and legal teams. The following six-step plan provides a practical framework that businesses of any size can adapt.

1. Gap analysis (T‑90 days). Audit your current invoicing process end-to-end. Identify every point where a paper or PDF invoice is generated, sent, received or archived. Map these against the new Greece e‑invoice requirements to identify gaps.
2. ERP and configuration changes (T‑75 days). Work with your ERP vendor or in-house IT team to activate the myDATA module, configure invoice-type mappings, and establish the API connection. Budget for potential vendor upgrade costs.
3. Vendor selection, if needed (T‑60 days). If your current ERP does not natively support myDATA integration, select a certified e‑invoicing middleware provider. Evaluate vendors on: AADE certification, API uptime guarantees, multi-country support, and customer-support responsiveness.
4. Supplier and customer onboarding (T‑45 days). Notify all B2B trading partners of your migration date. Provide clear instructions on how they will receive e‑invoices and what action is required on their side (e.g., system configuration to accept structured invoices).
5. Internal controls and approvals workflow (T‑30 days). Update your invoice-approval workflow to include a MARK-validation step. Ensure that no invoice is sent to a customer without a confirmed AADE MARK. Update segregation-of-duties policies accordingly.
6. Testing and pilot (T‑14 to T‑7 days). Run a controlled pilot with a small group of key trading partners. Verify that invoices are transmitted, MARKed, received and correctly posted in both your system and the recipient’s system.

Supplier Onboarding, Talking Points and Timeline

Updating supplier contracts and terms of business to reflect e‑invoicing obligations is a critical step that many businesses overlook. At a minimum, procurement and legal teams should address the following with each supplier.

• Communication of the mandatory start date and confirmation that the supplier’s system can receive structured e‑invoices.
• Agreement on the transmission channel, whether invoices will flow directly via myDATA, through a shared middleware provider, or via an alternative AADE-approved method.
• Contractual amendment to replace any clause requiring paper or PDF invoice delivery with a clause mandating structured e‑invoice delivery, including a fallback procedure if technical issues arise.
• Data-quality obligations, ensuring the supplier’s TIN, address and bank details are current and match AADE records.

Where suppliers are unable to receive e‑invoices by the mandatory date, businesses should document the situation and implement interim workarounds (such as issuing the structured e‑invoice to myDATA while providing a courtesy PDF copy), while actively supporting the supplier’s onboarding. For businesses managing complex international business relationships, aligning e‑invoicing terms across multiple jurisdictions adds an additional layer of contractual complexity that warrants specialist advice.

5. VAT Reporting, Record-Keeping and Audit Readiness

One of the most significant practical consequences of mandatory B2B e‑invoicing in Greece 2026 is its impact on VAT reporting. Because structured e‑invoices are transmitted to AADE in real time, the tax authority gains immediate visibility over transaction data, effectively creating a continuous audit trail. This fundamentally changes how businesses should approach e‑invoicing VAT reporting in Greece.

Impact on myDATA and VAT Returns

Under the new regime, invoice data reported through the e‑invoicing channel feeds directly into the myDATA digital books. Businesses must ensure that the data transmitted to AADE via e‑invoices is fully reconciled with their internal accounting ledgers and with the figures reported on periodic VAT returns. Any discrepancy between the real-time e‑invoice data held by AADE and the amounts declared on a VAT return is likely to trigger automated queries or audit flags.

Retention Periods

Greek tax law requires businesses to retain all tax-relevant documents, including e‑invoices, for a minimum period. While the structured e‑invoice data is stored within AADE’s myDATA system, businesses remain independently obligated to maintain their own records in a format that allows retrieval and verification. The retention period for invoices and supporting documents under the Greek Code of Tax Procedures is generally five years from the end of the tax year in which the invoice was issued. However, in cases involving ongoing audits, disputes or loss-carry-forwards, the retention obligation may extend further. Businesses should treat five years as the absolute minimum and apply longer retention where specific circumstances require it.

Reconciliation Checklist for Audit Readiness

6. E‑Invoice Penalties in Greece, Enforcement and Common Pitfalls

Failure to comply with the mandatory e‑invoicing obligations carries administrative penalties under the Greek tax code. While AADE has not published a single penalty schedule specific to e‑invoicing violations, the existing framework for invoicing infractions applies. Penalties for e‑invoice non-compliance in Greece may include the following.

• Failure to issue an invoice. Administrative fines calculated as a percentage of the transaction value, consistent with existing penalties for non-issuance under the Greek Code of Tax Procedures.
• Issuing a non-compliant invoice. Fines for invoices that do not meet the structured-data requirements (e.g., missing mandatory fields, absence of an AADE MARK).
• Late or failed transmission to myDATA. Penalties for delays in transmitting invoice data beyond the prescribed timeframe.
• Systematic non-compliance. Repeated violations may trigger a full tax audit and additional penalties, including potential suspension of VAT-refund claims.

Mitigation Checklist

1. Implement automated monitoring to flag any invoice that fails to receive an AADE MARK within the required timeframe.
2. Establish a documented remediation procedure for correcting failed transmissions within the shortest possible window.
3. Maintain a compliance log showing all e‑invoices issued, their MARK numbers, and any error-resolution steps taken.
4. Consider a voluntary self-correction approach if non-compliance is identified, early disclosure to AADE may reduce the severity of penalties.
5. Engage a Greek tax adviser to conduct a periodic compliance health-check, particularly in the first six months after your mandatory start date.

7. Practical Checklist, 10‑Point Implementation Plan for B2B E‑Invoicing Compliance

1. T‑90 days, Confirm your phase and deadline. (Owner: CFO / Tax Manager)
2. T‑90 days, Conduct an invoicing gap analysis. (Owner: CFO + IT Lead)
3. T‑75 days, Activate or procure an ERP myDATA module. (Owner: IT Lead)
4. T‑60 days, Select and contract a middleware vendor (if needed). (Owner: Procurement / IT Lead)
5. T‑45 days, Notify all B2B trading partners. (Owner: Procurement / Sales)
6. T‑30 days, Update supplier and customer contracts. (Owner: Legal / GC)
7. T‑30 days, Reconfigure internal approval workflows. (Owner: CFO / Internal Audit)
8. T‑14 days, Run a parallel testing pilot. (Owner: IT Lead + Finance)
9. T‑7 days, Final reconciliation check and go/no-go decision. (Owner: CFO)
10. Go‑live, Monitor, log and remediate any transmission errors immediately. (Owner: Finance + IT)

Red flags to watch for: API connectivity failures on go-live day, suppliers unable to accept structured invoices, mismatched invoice-type codes causing AADE rejections, and staff reverting to PDF invoicing out of habit.

Comparison Table, Reporting Obligations by Entity Type

8. Case Study, A Mid-Market Company’s Path to Mandatory B2B E‑Invoicing Compliance

Consider a hypothetical medium-sized Greek manufacturing company with €2 million in annual turnover and approximately 120 active B2B suppliers. As a Phase 1 entity, the company faced the early-2026 deadline. Here is how the implementation unfolded.

At T‑90 days, the CFO confirmed the company’s classification under Phase 1 and commissioned a gap analysis. The audit revealed that the company’s ERP system (a mid-tier platform widely used in Greece) had a myDATA module available but not yet activated. At T‑75 days, the IT team activated the module, configured invoice-type mappings and established the API connection to AADE’s test environment. By T‑60 days, parallel testing began with five key suppliers who had already migrated to structured e‑invoicing.

At T‑45 days, the procurement team sent formal notifications to all 120 suppliers, including a one-page FAQ explaining the transition. By T‑14 days, 95 suppliers had confirmed readiness; the remaining 25 were placed on a watch list with interim PDF-plus-myDATA procedures. On go-live day, the company processed 340 structured e‑invoices without a single AADE rejection, a result the CFO attributed to the 30‑day parallel testing period. Within 60 days, all 120 suppliers had completed onboarding, and the company’s VAT returns reconciled automatically with myDATA data for the first time.

Conclusion, Acting Now on Mandatory B2B E‑Invoicing in Greece 2026

The transition to mandatory B2B e‑invoicing in Greece 2026 is not a future concern, it is an operational reality that Phase 1 entities are already navigating and that Phase 2 businesses must prepare for immediately. The businesses that will manage this transition most smoothly are those that treat it as a cross-functional project involving finance, IT, legal and procurement from the outset, rather than a narrow tax-compliance exercise.

Early indications suggest that AADE intends to use the real-time data generated by e‑invoicing to enhance its audit capabilities significantly, making accurate and timely compliance more important than ever. Businesses that invest in proper ERP integration, thorough supplier onboarding and robust internal controls now will not only avoid penalties but will benefit from streamlined VAT reporting and reduced administrative overhead in the years ahead. For guidance on your specific compliance position, consider consulting a qualified Greek legal or tax adviser through our Greece lawyer directory or our broader global lawyer directory.

Sources

1. AADE (Independent Authority for Public Revenue), myDATA / e‑Invoicing Guidance
2. European Commission, eInvoicing in Greece (Digital Building Blocks)
3. Deloitte Greece, Mandatory B2B e‑Invoicing in Greece
4. EY Greece, Mandatory e‑Invoicing Tax Alert
5. KPMG TaxNewsFlash, Greece Implementation of Mandatory e‑Invoicing Postponed
6. Ecosio, Greece e‑Invoicing Requirements Explained
7. EDICOM, Greece Mandatory Electronic Invoice
8. RSM Global, Tax Alert: Mandatory e‑Invoicing Greece Implementation Timeline
9. Dynatos, Greece Postpones B2B e‑Invoicing