On 2 March 2026, Greece activated the first phase of its B2B e-invoicing mandate through the MyData platform operated by the IAPR (Independent Authority for Public Revenue, known in Greek as AADE). For international groups with a Greek subsidiary, branch, or VAT registration, this is not a distant regulatory concern — it is an active operational obligation, with penalties running since 3 May 2026 for Phase 1 entities.
This article unpacks what MyData actually requires — and why this system differs from traditional e-invoicing schemes such as Italy’s SDI or France’s PPF — so your ERP team knows exactly what to configure.
What MyData Is — and Why It Is Not “Just Another E-Invoicing System”
MyData (My Digital Accounting and Tax Application) is the IAPR’s central platform for real-time fiscal e-reporting (aade.gr/en/mydata). Its mission: to create a “digital accounting mirror” of every VAT-registered business directly inside the tax authority’s systems.
The key distinction that many IT directors miss: MyData is not a hub that routes invoices between trading partners. Invoices do not necessarily transit through MyData before reaching the buyer. Instead, the data from every invoice issued or received must be transmitted to MyData — in real time or near-real time for high-value transactions — and the IAPR returns a unique identifier in exchange: the MARK.
The system rests on three complementary layers:
- MyData e-Reporting: transmission of accounting and tax data to the IAPR for every invoice, credit note, or receipt. Mandatory since 2021 for large companies, progressively extended to SMEs.
- B2B e-Invoicing: since 2 March 2026, B2B invoices must be issued in a structured electronic format (EN 16931/Peppol) via an accredited provider (Y.PA.H.E.S.) or the AADE’s free tools.
- e-Transport: pre-notification of goods movements to the IAPR before any physical transport. A separate layer, outside the scope of this article.
The MARK: The Identifier Your ERP Must Manage
Every document submitted to MyData receives a MARK (Μοναδικός Αριθμός Καταχώρησης) — a 14-digit unique registration number assigned by the IAPR (clearvo.io). The MARK is the proof that the transaction has been registered in the tax authority’s systems.
Practical implications for your ERP:
- Without a valid MARK, an invoice is not legally compliant under Greek law.
- The MARK must appear on the document sent to the customer, alongside a QR code linking to the IAPR registry (mandatory since January 2024 for all PDF documents).
- The MARK also appears in the e-Books (digital accounting ledgers) that every entity must maintain up to date in MyData.
B2C (retail) invoices fall under document type 11.1 in the MyData nomenclature. Standard domestic B2B invoices use type 1.1; B2B services type 2.1; intra-EU sales type 1.2; exports outside the EU type 1.3. This classification code system — distinct from the accounting categories used in the UK, Germany, or the US — requires explicit mapping inside the ERP.
MyData Compliance Timeline 2024–2026
| Obligation | Scope | Effective Date |
|---|---|---|
| MyData e-Reporting (e-Books) | Large Greek companies | Since 2021 |
| MyData e-Reporting (e-Books) | All Greek SMEs | Since 2023 |
| B2G e-Invoicing via Peppol | Suppliers to the Greek State | Since September 2025 |
| B2B e-Invoicing — Phase 1 | Entities with 2023 turnover > €1 M | 2 March 2026 (penalties: 3 May 2026) |
| B2B e-Invoicing — Phase 2 | All other taxable entities | 1 October 2026 |
Phase 1 included a parallel-run adjustment period from 2 March to 3 May 2026. Since 3 May 2026, penalties are active for all Phase 1 entities (rtcsuite.com).
Which Foreign Companies Are in Scope?
This is the question most commonly raised by CFOs of international groups with Greek operations. The rule is straightforward:
You are within the MyData scope if your entity holds a Greek VAT number (EL prefix), whether through:
- a Greek-incorporated subsidiary (SA or Ltd under Greek law);
- a branch (permanent establishment in Greece);
- a fiscal representative (for foreign companies VAT-registered in Greece without a physical presence).
If your company invoices a Greek customer occasionally without being VAT-registered in Greece, you are not directly subject to MyData obligations. However, your Greek customer will need to declare the transaction on their side.
Intra-EU transactions have specific treatment: for sales to businesses established in other EU member states, the structured electronic format is not imposed on the foreign recipient (they may legally decline it). However, the transmission to MyData remains mandatory on the Greek side (edicomgroup.com).
The case of international groups with a Greek subsidiary is potentially the most complex: a Greek subsidiary of a UK, German, or US group must simultaneously satisfy MyData obligations on the Greek side AND, where applicable, feed cross-border flows into the parent company’s own e-reporting framework. Accounting mapping and flow coding must be planned ahead in the group ERP.
Affected Flows and Their ERP Treatment
Sales Invoices (Outbound e-Invoicing)
The invoice must be generated in a structured XML format (EN 16931 / Peppol BIS Billing 3.0), transmitted to the IAPR via an accredited Y.PA.H.E.S. provider or the free Timologio tool, and receive its MARK before being sent to the customer. The ERP must integrate this validation loop: issue the invoice, call the IAPR API (or the EDIP connector), retrieve the MARK, and embed it in the final PDF.
Purchase Invoices (Inbound e-Invoicing)
From Phase 2 onwards (October 2026), Greek Phase 1 companies are required to accept structured e-invoices from their Greek suppliers. The ERP must be able to receive Peppol-format invoices and validate the presence of the MARK — without which VAT deductibility may be challenged during an IAPR audit.
Digital Accounting Books (e-Books)
e-Books are the backbone of MyData even before the e-invoicing mandate. They include the general ledger, cash registers, fixed assets, and depreciation charges (pikon.com). Transmission is monthly or quarterly, with a deadline before the 20th of the following month. Since January 2024, wholesale invoices require real-time transmission.
Payroll Data
Social and payroll data flows through ERGANI, Greece’s social declaration system — separate from MyData. Do not conflate the two: MyData covers tax and accounting, ERGANI covers employment. An HRIS ERP deployed in Greece must feed ERGANI via its own connector, independently of the MyData configuration.
What Your ERP Must Cover to Be Compliant
Operational checklist by component:
- IAPR API connector or Y.PA.H.E.S. provider: a structural choice between building directly on the AADE API and delegating to an accredited provider. The most active Greek EDIPs include EntersoftONE (the first AADE-certified provider, formed from the Entersoft/SoftOne merger), alongside international players such as EDICOM.
- IAPR XML format generation from ERP documents (SD Billing for SAP, sales invoices for Odoo, AR Invoice for Dynamics).
- MyData classification coding: mapping document types (1.1, 1.2, 1.3, 2.1, etc.) and Greek VAT categories (24% standard, 13% reduced, 6% super-reduced) against ERP parameters.
- MARK retrieval and storage: the MARK returned by the IAPR API must be stored in the ERP and included in the invoice PDF alongside the QR code.
- Compliant archiving: the Greek legal retention period is a minimum of 5 years. Electronic archiving must guarantee document integrity and the presence of the MARK.
- Credit note handling: credit notes have their own document type (5.1) and must be transmitted separately to MyData with a reference to the original invoice.
Major ERP Support
SAP S/4HANA and SAP ECC: the SAP Document Compliance module (eDocument Cockpit) handles the MyData workflow natively — XML generation, IAPR API call, MARK retrieval. Compatible with ECC 6.0 and S/4HANA (pikon.com).
Oracle Fusion / ERP Cloud: Oracle Tax Reporting Cloud covers MyData e-reporting obligations. Verify that the “Greece Localization” module is activated in your instance.
Microsoft Dynamics 365 Finance: an ISV partner localization is required (no Microsoft-native MyData localization at time of writing). Several certified partners offer extensions for the Greek market.
Odoo: third-party MyData modules are available on the Odoo Apps Store. Verify that the module supports your deployed Odoo version and that the module vendor is either directly AADE-accredited or routes transactions through a certified EDIP.
Pitfalls for International Groups
Dual regulatory obligations: a Greek subsidiary of an international group is subject to MyData (Greece) and must also, where applicable, feed the parent company’s own e-reporting framework. Cross-border intra-group flows must be correctly coded in both systems — with classification schemes that do not map natively to each other.
Classification code mapping: MyData document types (1.1, 1.2, etc.) have no direct equivalents in UK, US, or German chart-of-accounts structures. Specific mapping work is required during ERP configuration, especially for intra-group transactions or self-billing arrangements.
Self-billing invoices: they have specific treatment in MyData. The company receiving the service may issue the invoice on behalf of the supplier, provided both parties have formally agreed to this arrangement. The document type and associated codes differ from standard invoices.
Penalties are asymmetric: for transactions with VAT, the penalty is 50% of the undeclared VAT amount (saft-validator.com). For non-VAT transactions, fixed fines of €500 or €1,000 per infringement apply depending on the type of accounting maintained. Penalties have been active for Phase 1 companies since 3 May 2026.
Fiscal representatives play a key role for foreign companies without a permanent establishment but VAT-registered in Greece: they are often contractually responsible for MyData compliance, which means integrating them into your transmission workflow.
Five Steps to Achieve Compliance
Step 1 — Map your Greek entities: identify every entity holding an active EL number (subsidiary, branch, fiscal representative) and its 2023 turnover to determine whether it is Phase 1 (> €1 M) or Phase 2 (all others, deadline October 2026).
Step 2 — Audit affected invoice flows: B2G (already active via Peppol), domestic B2B, intra-EU sales, non-EU exports, purchase invoices, self-billing, credit notes. Each type has its own MyData code and transmission deadline.
Step 3 — Choose your transmission method: direct IAPR API (recommended for high volumes with a supported international ERP) or delegation to an accredited EDIP (faster to implement for mid-size structures). For very small Greek group entities: the free AADE tools (Timologio, myDATAapp) are sufficient for low volumes.
Step 4 — Configure classification codes in the ERP: work to be done in collaboration with the Greek accounting team or local tax advisor. The mapping between your ERP VAT codes and MyData categories (1 to 8) must be documented and validated before go-live.
Step 5 — Test on the IAPR sandbox environment: the AADE provides a test environment. Validate every flow type before production deployment, and retain MARK logs for each test — they serve as evidence in the event of an audit.
For broader context on the European regulatory landscape, see our analysis of Peppol as a shared e-invoicing infrastructure across Europe, our deep-dive into VIDA and the EU digital VAT roadmap 2025–2035, and our overview of e-invoicing in Central and Eastern Europe (KSeF, RTIR, e-Factura).
