Greece's mandatory B2B e-invoicing enters phase two in October 2026
Greece will require all remaining domestic businesses to use structured e-invoicing from 1 October 2026, building on the myDATA framework that began phase one in March.
Greece’s mandatory B2B e-invoicing regime enters its second phase on 1 October 2026, when all remaining Greek-established businesses must begin using structured invoices. The mandate builds on the existing myDATA digital reporting framework and requires invoices to be transmitted through accredited providers or AADE’s free tools, validated, and returned with a unique MARK identifier and QR code.
Greece will require all remaining domestic businesses to adopt mandatory structured e-invoicing from 1 October 2026. The second phase extends the mandate that began on 2 March 2026 for larger businesses, bringing the full population of Greek-established firms into the regime.
The October deadline is not a simple format change. It introduces a controlled digital process in which invoice creation, transmission, validation and tax reporting become tightly integrated. Businesses should treat this as a fundamental shift in how invoices flow through their accounting systems, not merely a new file format.
How the Greek model works
Greece’s e-invoicing system builds on myDATA, the country’s existing digital accounting and tax reporting framework. Structured invoices are transmitted electronically through accredited service providers or AADE’s free invoicing tools. After validation, each invoice receives a unique registration identifier called a MARK and an associated QR code.
For businesses with significant transaction volumes, manual invoicing through a government application is not practical. Integration between the ERP system and an accredited provider is normally required to automate invoice creation, transmission and processing. The solution must also capture validation results, the MARK, QR code and document status, and return them to the accounting system.
What phase two businesses must prepare
Businesses entering phase two should complete several critical tasks before October:
- Determine the scope of transactions and legal entities affected, including domestic B2B sales, relevant exports, credit notes, debit notes, advance payments and intercompany transactions
- Review and clean master data: customer tax numbers, addresses, legal names, invoice classifications, product information and tax codes
- Map ERP tax codes and invoice types to myDATA classifications and document categories
- Test the complete invoice lifecycle from creation through delivery and accounting reconciliation
- Verify error handling for incomplete customer data, connectivity failures, myDATA rejections and invoice corrections
- Establish clear ownership across tax, finance, accounts receivable, IT and customer service
Testing should not focus only on straightforward domestic sales invoices. Businesses must verify that their solution handles less frequent transactions, negative scenarios and the full end-to-end process including MARK retrieval, QR-code generation and automated error management.
Broader compliance context
Mandatory B2B e-invoicing is one layer of Greece’s digital tax environment. Businesses may also face myDATA reporting requirements, B2G e-invoicing mandates and digital delivery-note rules for goods movement. Each has its own technical and operational requirements.
Companies should avoid treating the October mandate as an isolated technical project. Invoice data, goods-movement data, accounting entries and VAT reporting must remain consistent across all systems. Differences between these data sets may create reconciliation problems and increase the risk of queries from Greek tax authorities.
Timeline and transition
Phase two is accompanied by a transition period extending through the end of 2026. However, a compliant solution must be operational before invoices within scope are issued. Businesses should not interpret the transition period as a reason to postpone preparation.
Multinational groups that issue Greek invoices from a central or regional ERP environment face particular complexity. The group must ensure that local Greek requirements are integrated into global order-to-cash processes without disruption.
Businesses within scope should use the remaining time to move from design to testing and from testing to production readiness. Waiting until October to test the full process risks rejected invoices, customer disputes, delayed collections and inconsistencies in myDATA records.