Connecting an e-shop to myDATA means every order issues the correct tax document on its own and sends it automatically to the Greek tax authority (AADE), where it receives a unique registration number called MARK. This happens through a certified e-invoicing provider or through the software you already use — with nothing typed by hand.
From 1 October 2026, electronic invoicing becomes mandatory for all remaining businesses in Greece, regardless of turnover. If you run an e-shop and still issue documents manually, this guide shows you what to do and in what order.
Want this sorted once and for all? Book a free 30-minute invoicing audit and see exactly what your e-shop is missing.
Table of Contents
What myDATA is and why it affects your e-shop
myDATA is the AADE’s digital platform where the income and expenses of every Greek business end up. It works like a set of electronic books: whatever you issue, the tax office sees almost immediately.
Every document that arrives there receives a unique number, the MARK. Without that number, an invoice or receipt is not considered valid.
For an e-shop this matters in practice. Orders arrive around the clock, including weekends, so manual issuance quickly becomes a burden.
What the integration gives you:
- The document is issued the moment the order is placed, without you having to remember to do it.
- The customer receives it by email alongside the order confirmation.
- Your accountant gets clean data, and the monthly “send me the receipts” routine disappears.
- Errors in VAT rates, document series, and numbering drop sharply.
What changes in 2026: the dates you need to know
Mandatory electronic invoicing in Greece arrives in two phases.
| Date | Who it affects | What applies |
|---|---|---|
| 2 February 2026 | Businesses with gross revenue above €1 million (2023 tax year) | Phase A: mandatory B2B e-invoices through a certified provider |
| 1 October 2026 | All remaining businesses, regardless of size | Phase B: small businesses come in |
| 1 October – 31 December 2026 | Businesses entering Phase B | Transition window for adaptation |
| 1 January 2027 | Everyone | Full application, no grace period |
The obligation mainly covers business-to-business transactions and sales to countries outside the European Union. Sales to private consumers are not covered by the e-invoicing mandate.
There is a catch, though. Even if you sell only to consumers, your retail data still goes to myDATA. The integration affects you either way.
Business chambers have asked for a postponement to March 2027. Until something official is published, work with the dates that apply today.
Which documents an e-shop issues
Before choosing a solution, you need to know exactly what you issue. Most Greek e-shops produce three or four types.
| Type of sale | Document | When it is needed |
|---|---|---|
| Sale to a consumer in Greece | Retail receipt | The majority of orders |
| Sale to a business with a VAT number | Sales invoice | When the customer asks for an invoice |
| Sale to a consumer in another EU country | Receipt with destination-country VAT (OSS scheme) | Once you pass the €10,000 threshold |
| Refund or cancellation | Credit note | After the original document has been issued |
The credit note is where most shop owners get confused. Once a document has gone to myDATA, you do not delete it — you issue a credit note against it.
Does an e-shop need a cash register?
No, it is not required. An e-shop selling exclusively online can issue retail receipts electronically through a certified provider, with no cash register and no fiscal device.
The provider handles the marking and the transmission to AADE. The receipt reaches the customer as a PDF, by email, within seconds of the order.
If you also run a physical shop with a till, the cash register stays there. The two flows can coexist, as long as you keep separate document series for each.
The four integration routes — and which one suits you
| Route | How it works | Best for | Indicative cost |
|---|---|---|---|
| Certified provider | The e-shop sends the order to the provider, who issues the document and transmits it to AADE | E-shops with steady order volume | From ~€10–20 per month |
| WooCommerce plugin | A plugin connects the store directly to myDATA or to a provider | WooCommerce stores with simple invoicing | ~€80–150 per year |
| Commercial software or ERP | Orders flow into the software and from there to AADE | Businesses with stock control and a physical shop | Depends on the software |
| Free AADE tools (timologio, myDATAapp) | You enter documents by hand | Very low volume, a few orders a month | No cost |
The rule of thumb is simple. Below 20–30 orders a month, the free AADE tools hold up fine. Above that, an automated provider integration pays for itself within the first month.
The same logic applies to reliability. A plugin that fails during a peak sales period costs you more than the subscription you were trying to avoid.
Not sure which route fits? Send us your e-shop details and we will recommend the option with the lowest cost and the least maintenance.
Step by step: how the integration is done
Step 1: Talk to your accountant first
Before you touch anything technical, you need answers to three questions: which VAT rates apply to your products, whether you sell outside Greece, and which document series you will use.
That twenty-minute conversation saves weeks of corrections later.
Step 2: Choose a provider or solution
Check three things: that it is certified by AADE, that it supports your platform (WooCommerce, Shopify, custom), and that support is available in a language your team can work in.
Step 3: Generate your myDATA credentials
Log into the AADE myDATA platform with your TaxisNet codes and create a dedicated user for the e-shop. From there you get two values: a User ID and a Subscription Key.
You give these two to your provider or enter them in the plugin settings. Never send them by plain email — use a secure method.
Step 4: Declare your document series
Each document type needs its own series and its own numbering. Declare a separate series for online sales so they never mix with the physical shop.
Step 5: Set VAT per product
VAT is declared on each product, not once for the whole store. Books, food and services carry different rates, so a single shop-wide setting will produce incorrect documents.
Do not forget shipping charges and discounts. Both affect the calculation.
Step 6: Test in the sandbox environment
AADE provides a test environment. Run at least five scenarios through it before going live:
- A simple consumer order
- An order with a VAT number and a full invoice
- An order with two different VAT rates
- A full refund
- A partial refund of a single item
Step 7: Go live and watch the first few days
For the first two weeks, check daily that every order received a MARK. Set up an email alert for any document that fails to transmit.
How fast must documents be sent?
Transmission deadlines differ depending on how you work.
| Route | Deadline |
|---|---|
| Through a provider or business software | Real time, on issue |
| Retail through a connected cash register | Between 1 minute and 24 hours |
| Manually, via the special form | By the following day |
| Accounting entries | By the 20th of the following month |
In practice, with a proper integration you never need to remember any of this. The system transmits on its own at the moment of sale.
How much does myDATA integration cost?
The cost splits into two parts: the one-off setup and the subscription that runs every month.
- Setup and testing: usually €200–500 for a typical WooCommerce store, depending on how complex your invoicing is.
- Provider subscription: from roughly €10 per month for low volume, scaling with usage.
- Plugin licence: €80–150 per year if you go down that route.
- Complex cases: EU sales, subscriptions or marketplace channels push the setup cost higher.
Compare that with the alternative. Fifteen minutes a day on manual issuing is about seven hours a month — and that is before counting the errors.
If you are planning your wider budget, see our guide on how much a professional website costs in Greece.
The six mistakes that cost you fines
- Leaving it until the last minute. Providers fill up as the deadline nears and implementation times stretch.
- A wrong VAT rate on one product. An error that goes unnoticed for months produces dozens of incorrect documents.
- Cancelling instead of issuing a credit note. Once the document has been transmitted, a credit note is the only correct route.
- No monitoring of failures. Without alerts, you will hear about it from your accountant three months later.
- Incomplete details for business customers. Ask for the VAT number and registered address at checkout, not by email afterwards.
- Forgotten orders that were never completed. Cancelled or unpaid orders should not generate documents.
Fines for non-transmission start at €100 per document for single-entry books and reach €500 for double-entry books. Confirm the current figures with your accountant, as they change.
Frequently asked questions
Can I connect Shopify to myDATA?
Yes. Apps and providers cover Shopify, though the choice is narrower than on WooCommerce. Complex cases usually need a provider sitting between the store and AADE.
What if I also sell to other EU countries?
Up to €10,000 in annual sales to EU consumers, you charge Greek VAT. Above that, you enter the OSS scheme and charge the customer’s country rate. Pick a solution that supports this from the start.
Do I lose documents if my site goes down?
No, not if you work with a provider. Documents are stored with the provider and in myDATA, independently of your own site.
Do I need to print receipts?
No. An electronic receipt carrying a MARK is fully valid and can be sent by email alone.
Can I set this up myself?
If you run WooCommerce with a handful of products and a single VAT rate, yes. With multiple rates, sales outside Greece or subscriptions, a developer will save you considerable time.
How to start this week
Connecting an e-shop to myDATA is not a large project, but it has a deadline. The closer 1 October 2026 gets, the harder it becomes to find an available developer.
Three things this week: talk to your accountant, write down which documents you issue, and request two quotes from providers. With those in hand, the rest of the setup takes a few days.
Once invoicing is handled, move on to the part that actually brings sales: being found online. Our guide to local SEO and Google Business Profile is a good starting point.
Next step Book a free 30-minute call with the team at The Dev Alley. We will review your e-shop, work out which documents you need and which solution costs least — no commitment.
This article is for information only and does not constitute tax advice. For your own situation, consult your accountant.
