Greece myDATA: The Complete Guide for Businesses

Greece introduced myDATA (My Digital Accounting and Tax Application) as part of AADE's (Ανεξάρτητη Αρχή Δημοσίων Εσόδων — the Independent Authority for Public Revenue) drive to digitise its VAT administration. It is not an optional accounting platform. It is a mandatory real-time reporting obligation that applies to every business registered for Greek VAT, regardless of size or country of establishment.

If you invoice Greek business customers — or receive invoices from Greek suppliers — you are likely in scope. This guide explains exactly how myDATA works, what the MARK identifier is, who needs to comply and when, and what your technical integration needs to look like.

What is myDATA?

myDATA is a real-time digital ledger operated by AADE, Greece's tax authority. Every business that is registered for Greek VAT must transmit its income and expense documents to myDATA, which then returns a MARK (Μοναδικός Αριθμός Καταχώρησης — Unique Registration Number) identifier for each document. That MARK must appear on the invoice.

The system works in both directions:

• Income documents (invoices you issue): transmitted to myDATA at the point of issuance. myDATA validates the document and returns a MARK. The MARK is the legal proof that the invoice has been registered with the tax authority.
• Expense documents (invoices you receive): AADE expects the MARK to be present on incoming invoices. Your accounting records must reconcile against the MARKs reported by your suppliers.

Unlike Italy's clearance model — where the tax authority must approve an invoice before it is legally delivered to the buyer — myDATA is a reporting model. You can deliver the invoice to your buyer immediately, but you must report the transaction data to AADE within the required timeframe.

Who is in scope?

myDATA applies to all businesses that:

• Are registered for VAT in Greece (Greek VAT number, starting with EL)
• Issue or receive taxable invoices under Greek VAT rules
• Have a permanent establishment or fixed place of business in Greece — OR are foreign businesses registered for Greek VAT

There is no SME exemption for the reporting obligation itself. The phased rollout that applied during 2021–2023 is complete — all VAT-registered entities are now in scope.

Non-established businesses: If you are registered for Greek VAT but have no establishment in Greece (for example, a UK or US company registered for Greek VAT because you supply Greek B2B customers), you are still required to transmit your Greek invoices to myDATA.

How myDATA works: the two-step workflow

For each invoice you issue to a Greek business customer, the workflow is:

1. Generate the invoice in your billing system with all required fields (see below).
2. Transmit to myDATA via AADE's API or through an accredited provider. The transmission includes structured invoice data: supplier/buyer identification, line items, tax classification, and totals.
3. Receive the MARK. AADE returns the MARK identifier, typically within seconds. The transmission also returns a UID (unique identifier) if the invoice is transmitted via the Peppol network.
4. Include the MARK on the invoice before delivering to your buyer. An invoice without a MARK is not legally valid in Greece.
5. Deliver to buyer. The buyer's accounting system should record the MARK for reconciliation with their own myDATA submissions.

The reporting window is within 24 hours of issue for most invoice types. For retail transactions, periodic aggregate reporting is permitted. For B2B invoices, same-day or next-day transmission is standard practice.

The MARK identifier

The MARK (Μοναδικός Αριθμός Καταχώρησης) is AADE's unique registration number for each document transmitted to myDATA. It is a 14-digit number assigned sequentially per entity.

The MARK serves three purposes:

• Proof of transmission: the existence of a MARK proves the invoice was reported to AADE at or near the time of issuance.
• VAT return reconciliation: AADE's systems match MARKs from income transmissions against VAT returns. An invoice with no MARK may trigger a query or flag the VAT return for review.
• Buyer verification: buyers can verify the MARK of an incoming invoice against the myDATA ledger, confirming the supplier reported the transaction.

The MARK must appear on the face of the invoice — typically in the reference or remarks field. Your invoicing system needs to support inserting the MARK after receiving it from myDATA before rendering the final document.

Invoice classification: the myDATA document types

myDATA uses a classification system for both income and expense documents. Each invoice must be classified with the correct document type and VAT category. The main income document types are:

The classification must be transmitted with the invoice data. Incorrect classification is one of the most common errors in myDATA submissions — in particular, misclassifying intra-community supplies (which affect the VAT treatment) or using the wrong type for credit notes.

VAT categories in myDATA

Each line item must also carry a VAT category code:

• Category 1 — Standard rate (24%)
• Category 2 — Reduced rate (13%)
• Category 3 — Super-reduced rate (6%)
• Category 4 — Zero-rated (0% — includes intra-community and export)
• Category 5 — Exempt from VAT
• Category 7 — Reverse charge
• Category 8 — Outside scope (non-taxable transactions)

For businesses using Clearvo's e-invoicing API, these categories map directly to the EN16931 tax codes (S, AA, AE, E, K, G) used across all 32 countries — you classify the line item once in your product catalogue, and Clearvo translates to the correct myDATA category for Greek submissions.

Peppol and myDATA

Greece is also part of the Peppol network. Businesses can receive Peppol invoices (BIS Billing 3.0 format) directly into their ERP systems. The YPAHES service provider acts as the Greek government's reference point for Peppol-based B2B e-invoicing alongside myDATA.

When an invoice is transmitted via Peppol to a Greek buyer, myDATA also receives the transmission — the UID and MARK are generated at the point of Peppol routing. For businesses using Clearvo's certified Peppol Access Point (AP ID PIE001162), this means both Peppol delivery and myDATA reporting happen in a single API call, with no separate AADE integration required.

What data must be transmitted?

Each myDATA submission for an income invoice must include:

• Supplier VAT number (EL prefix for Greek businesses)
• Buyer VAT number (required for B2B; aggregate for B2C retail)
• Invoice number and issue date
• Document type code (1.1, 2.1, etc.)
• Line items with description, quantity, unit price, discount
• VAT category per line and VAT amount
• Total net amount, total VAT, total gross amount
• Currency (EUR for domestic; original currency + EUR equivalent for foreign currency invoices)

For intra-community supplies (type 1.2 and 2.2), the buyer's EU VAT number must be validated via VIES before transmission. AADE cross-references the VIES validation against the zero-rate classification.

Common errors and how to avoid them

1. Transmitting after delivery

The most frequent compliance gap is treating myDATA transmission as an afterthought — generating the invoice, sending it to the buyer, and then reporting to AADE hours or days later. This leaves a window during which the invoice has been delivered but has no legal standing in the AADE ledger. Automate transmission at the point of invoice generation, before delivery.

2. Missing MARK on the delivered invoice

The MARK must appear on the invoice the buyer receives. Workflows that generate the final PDF before receiving the MARK will produce invalid documents. Your billing system must wait for the MARK before rendering the final invoice.

3. Incorrect document type for credit notes

Credit notes in myDATA must reference the MARK of the original invoice they are correcting (type 5.1 — associated credit note). Unassociated credit notes (type 5.2) are a separate category with different reconciliation rules. Using the wrong type causes reconciliation failures in the buyer's expense ledger.

4. Wrong VAT category for reverse charge

Services provided by non-Greek EU businesses to Greek VAT-registered buyers are subject to reverse charge (Category 7). The supplier should not charge Greek VAT — the buyer self-accounts. Incorrectly charging 24% on an intra-community service creates a VAT position that neither party can recover cleanly.

The practical checklist

1. Confirm your Greek VAT registration is active and that your EL VAT number is valid in VIES.
2. Audit your invoice data fields: do your invoices include buyer VAT number, document type, per-line VAT category?
3. Choose a transmission method: direct AADE API integration, or through a provider like Clearvo that handles the API call and returns the MARK.
4. Update your invoice template to include a MARK field that populates after the API call returns.
5. Update credit note workflows to pass the original invoice MARK as the associated reference.
6. Test in the AADE sandbox (production-equivalent environment) before switching to live submission.
7. For Peppol deliveries: ensure your Access Point handles the myDATA transmission as part of the Peppol routing — you should not need to make a separate API call to AADE.

How Clearvo handles myDATA

Clearvo connects directly to the AADE myDATA API as part of its multi-country e-invoicing API. When you submit a Greek invoice via Clearvo:

1. Clearvo translates your invoice data from the Common Data Model into the myDATA XML format.
2. Clearvo transmits to AADE and receives the MARK.
3. Clearvo returns the MARK in the API response so your system can include it on the final invoice document.
4. For Peppol-registered buyers, Clearvo also routes the invoice via its certified Peppol Access Point (AP PIE001162) — myDATA registration and Peppol delivery in a single call.

The Clearvo sandbox simulates real AADE behaviour — submissions return a sandbox MARK immediately, letting you test the full invoice workflow including MARK insertion before you go live.

If you are already managing Italian, Polish, or Romanian e-invoicing through Clearvo, adding Greece is a configuration change, not a new integration — the same API endpoint handles all countries.

Frequently asked questions

Does myDATA apply to foreign businesses invoicing Greek customers?

It depends on your VAT position. If you are registered for Greek VAT (with an EL number), your Greek invoices must go through myDATA. If you are not registered for Greek VAT — for example, a UK business supplying digital services to Greek consumers under OSS — myDATA does not apply to you directly, though your Greek buyer may need to handle their own expense classification.

Can I submit invoices to myDATA retroactively?

AADE permits retroactive submission for certain document types, but a late MARK on a delivered invoice creates a compliance risk — the invoice was legally incomplete at the time of delivery. AADE can apply penalties for late transmission. For ongoing compliance, real-time or same-day transmission is required.

Is myDATA the same as e-invoicing?

myDATA is a reporting obligation, not a full e-invoicing mandate. You can still send a PDF invoice to your Greek buyer — but you must also transmit the transaction data to AADE and include the MARK on that PDF. Greece's approach differs from Italy's (where the invoice must pass through SDI before it can be delivered at all). However, Greece is part of the Peppol network, and Peppol B2B e-invoicing is available for businesses that want fully structured electronic exchange.

What happens if I miss the myDATA transmission?

AADE can issue penalties for late or missing transmissions. More significantly, the absence of a MARK on an invoice creates problems for your buyer — they cannot properly record the expense document in their own myDATA ledger, which can trigger queries when AADE cross-references income and expense records across the supply chain.

Where can I test my myDATA integration?

AADE operates a sandbox (test) environment for myDATA. Clearvo's sandbox also simulates myDATA responses — submissions return a test MARK immediately, allowing you to validate your full invoice workflow end-to-end before going live.