Greek myDATA e-invoicing

What is this page about: How to set up myDATA on a Greek entity, the document numbering and VAT rules it enforces, how tax codes are translated for the Greek tax authority, and how credit notes link back to accepted invoices.

This article covers what is specific to myDATA. The wizard, registration statuses and EDIFACT codes are the same everywhere and are explained in E-invoicing in Light.

# At a glance

# On this page

• What is myDATA?
• Getting registered
• What you need to fill in
• Document numbering
• VAT rates
• Tax codes and what they become
• Credit notes and linked invoices
• Limits
• Frequently Asked Questions
• Related articles

Quick summary: myDATA is Greece's mandatory real-time reporting system. Getting set up is a five-step process. You authorise our e-invoicing provider in the Greek tax portal, send us your company details, we register you with the provider, you sign a service agreement, and we confirm when you are live. Only then can invoices be submitted. After that, every tax code you use needs an EDIFACT code, document numbers need a letter-bearing series followed by digits, and only the approved Greek VAT rates are accepted.

# What is myDATA?

myDATA (My Digital Accounting and Tax Application) is the digital reporting system run by Greece's Independent Authority for Public Revenue (AADE). Any business issuing invoices in Greece has to report them through it.

It reports rather than delivers. Your customer receives their invoice the way they always have, because Light emails them the PDF. What goes to myDATA is a structured record of the same document. When AADE accepts it, the document receives an IAPR MARK, a unique reference proving it was reported. Light submits invoices and credit notes as soon as you finalise them.

myDATA reports to the tax authority rather than delivering to your customer, so a Greek entity has no e-invoice address or EAS code. That is expected. For sending invoices to customers in other EU countries, see E-invoicing: Peppol and myDATA. A Greek entity can hold both registrations, and each customer's own network setting decides which route their invoice takes.

# Getting registered

Switching myDATA on takes more than a toggle in Light. Greek law requires you to formally authorise an accredited e-invoicing provider with the tax authority, and to sign a service agreement with them. Some of that happens in the Greek tax portal and some of it happens on paper, so plan for it to take weeks rather than minutes.

Here is the whole sequence, and who does what.

# Step 1. Authorise the provider on myTAXISnet

This one is yours to do, in the Greek tax portal, and nothing else can start until it is done.

1. Log in to myTAXISnet
2. Open the Authorizations tab (Εξουσιοδοτήσεις) on the left-hand side
3. Scroll to Providers of E-invoicing (Πάροχοι Ηλεκτρονικής Τιμολόγησης)
4. Click New (Νέα)
5. Enter the provider's VAT number and submit the authorisation

Ask us for the provider's VAT number before you start, and tell us the date you submitted the authorisation so we can match it up on our side.

# Step 2. Send us your company details

We need all of the following to prepare your registration. Gather them before you get in touch, because a missing field holds up the whole chain.

# Step 3. We register you with the provider

Nothing for you to do here. We pass your details on and the provider sets up your registration.

This is also the point to add myDATA in Light, if you have not already: open the entity, click + Add in the E-invoicing section, and choose myDATA. myDATA has no document to upload and no verification step in the wizard. The registration shows as In-progress and stays there until everything below is finished.

# Step 4. Sign the service agreement

The provider prepares a service provision contract, pre-filled from the details you gave us in step 2, and sends it to us. We pass it to you. Your legal representative reviews it, signs it, and returns the signed copy, which we send back to the provider.

This is the step that usually holds things up. The contract needs a real signature from someone empowered to sign for the company, and it often sits waiting for that. If you know your myDATA go-live date, start the process well ahead of it.

# Step 5. Go live

Once the signed contract is back with the provider, they complete the onboarding and confirm that your entity is active. We then mark the registration Active in Light, and finalised invoices and credit notes start being submitted automatically.

Your Greek tax advisor or your tax office can confirm which registration details are correct for your business if you are unsure about any of them.

# Who does what, at a glance

# What you need to fill in

This section covers what Light itself needs. The separate list of company details we need from you in order to register you with the provider is in step 2 above.

Two moments matter here, and the second one catches people out.

# To add myDATA in Light

# To send an invoice

The customer-side fields are the more common cause of a blocked invoice. If an invoice will not submit, check the customer record before the entity.

# Document numbering

myDATA needs every document number to be a series followed by a serial number. The series must contain at least one letter or digit that is not part of the trailing number, and the serial is the digits at the end.

These are illustrative examples, not real account data.

Separators are removed from the series. Hyphens, slashes and spaces are stripped before submission, so INV-2024-001 is reported as series INV2024, serial 001. That means two numbering schemes which look different to you, INV-2024-001 and INV/2024/001, arrive at AADE as the same series. Pick one scheme per document type and stay on it.

A purely numeric document number like 12345 is rejected, because it has no series.

# VAT rates

myDATA accepts a fixed set of VAT rates, and they differ between the mainland and the reduced-rate islands.

The rate on your tax code has to match one of these exactly. Anything else is rejected with an error naming the rate. Light applies no rounding or nearest match, so a tax code at 23% fails even if it is correct for some other purpose.

This restriction applies to standard-rated tax codes only. Exempt, zero-rated, reverse-charge and similar treatments are handled through their EDIFACT code instead, and carry no rate.

# Tax codes and what they become

Every tax code used on a myDATA document must have an EDIFACT code. Without one, the invoice is blocked.

Set it at Settings (gear icon) → Tax codes: create or open a tax code, choose the EDIFACT (optional) code, and save.

Each code becomes a specific myDATA classification. Where VAT is not charged, myDATA requires an exemption category as well, and Light supplies it.

A line with no tax code at all is reported as exempt, category 27.

The EDIFACT dropdown also contains codes for the Spanish territories (IGIC and IPSI). They are not relevant to Greek invoicing, so do not use them on a tax code you will use on a myDATA invoice.

# Credit notes and linked invoices

myDATA distinguishes two kinds of credit note, and Light picks the right one based on whether you linked the credit note to an invoice.

Linked (type 5.1, Associated). The credit note references the original invoice by its IAPR MARK. That means the original has to have been accepted by AADE first. If you finalise the credit note before the invoice has come back accepted, you will get an error asking you to try again shortly.

Standalone (type 5.2, Non-Associated). A correction not tied to a specific invoice. Fully supported, with no waiting.

Credit notes carry a nominal bank transfer as their payment instruction, since a reversal has no real payment method and myDATA requires the field.

# Limits

• Reporting only. myDATA does not deliver anything to your customer and does not receive supplier invoices. Your customer still gets the PDF from Light.
• Greek entities only. myDATA appears in the wizard only for entities registered in Greece.
• The VAT-rate list is closed. Any rate outside the six above is rejected.

# Frequently Asked Questions

Is registration automatic once I fill in my entity details?

No, and this is the biggest difference between myDATA and the other networks. Filling in your entity and adding myDATA in the wizard is only one part of step 3. You also have to authorise our provider in myTAXISnet, give us your company details, and sign a service agreement. See the five steps above.

How long does it take?

Weeks rather than minutes, and most of the elapsed time is usually spent waiting for the service agreement to be signed. Start well before the date you need to be issuing invoices.

My registration has been In-progress for a long time. Is something wrong?

Probably not, but check where you are in the five steps. The most common reason is that the service agreement in step 4 has not been signed and returned yet. Contact support and we will tell you which step you are on.

Do I have to do anything in the Greek tax portal myself?

Yes. Step 1, authorising the provider on myTAXISnet, can only be done by you. We cannot do it on your behalf.

What happens if I use a VAT rate that is not approved for Greece?

The invoice is rejected, and the error names the rate that was not accepted.

Can a document number be purely numeric, like "12345"?

No. It needs a series in front of the digits.

Why did my document number lose its dashes?

myDATA does not accept separators inside a series, so they are removed before submission. The document keeps its original number everywhere else in Light.

Do all tax codes need an EDIFACT code?

Any tax code used on a myDATA document does. Without one the invoice is blocked, despite the field being labelled optional.

Can I issue a credit note that is not linked to a specific invoice?

Yes. Those are type 5.2, and they are supported alongside linked ones.

Why will my credit note not finalise?

If it is linked to an invoice, the invoice has to be accepted by AADE first. Wait a few minutes and try again.

What is the difference between myDATA and Peppol?

myDATA reports your invoices to the Greek tax authority, and Peppol delivers invoices to customers. They do different jobs, and a Greek entity trading across borders often needs both.

# Related articles

• E-invoicing in Light
• E-invoicing: Peppol and myDATA
• Italian SDI e-invoicing
• Tax and VAT Configuration
• Sending Invoices