- myDATA is AADE’s platform for receiving business transaction data.
- It does not replace statutory accounting records or proper bookkeeping.
- Issuing a legal invoice and transmitting its data are different actions.
- myDATA transmission is not the same as electronic invoicing through an officially recognised channel.
- AADE’s free timologio application issues documents and transmits them at the same time.
- The Special Registration Form transmits data; it does not issue invoices and is subject to usage limits.
- myDATA data is linked to VAT returns and the E3 business tax form.
- An expense is not tax-deductible merely because it appears in myDATA.
1. What is myDATA?
myDATA stands for my Digital Accounting and Tax Application. It is the digital platform operated by Greece’s Independent Authority for Public Revenue (AADE) to receive data from invoices, retail receipts and accounting entries. It provides the tax authority with a structured view of a business’s revenue, expenses and tax classifications.
The Detailed Transactions Book records transmissions relating to the business. The Summary Book shows aggregated monthly and annual results.
The underlying invoice, contract, payment and other evidence remain relevant.
2. Who is covered?
The obligation generally covers entities falling under Article 1 of Greek Law 4308/2014, regardless of size or bookkeeping method, subject to the statutory exceptions and special cases.
In practical terms, this includes a service freelancer, doctor, online teacher, consultant, sole-trader shop and small company. myDATA is not limited to large organisations and does not begin only after a turnover threshold is crossed.
3. What is transmitted to myDATA?
The platform normally receives an invoice summary, rather than the complete customer-facing document. Data includes essential counterparty information, document type and number, issue date, net value, VAT, withholding taxes, other taxes or charges and the prescribed income or expense classifications.
Revenue, expense data and year-end adjustment entries may all feed into myDATA. Every valid transmission receives a unique registration number known as a MARK.
The full commercial description of every product or service is not necessarily transmitted in the same detail in which it appears on the invoice.
4. Issuing and transmitting are not the same
Issuing means creating the legal invoice or retail receipt with the required information. Transmission means sending the prescribed data from that document to AADE.
Some applications perform both steps together. Other methods deal only with transmission. AADE’s Special Registration Form is the clearest example: it sends the data of a document that has already been legally issued elsewhere; it does not create the customer’s legal invoice.
5. How can documents be transmitted?
The main channels are a certified electronic-invoicing provider, AADE’s timologio application, a connected ERP or accounting/commercial system, the Special Registration Form where permitted, and fiscal electronic mechanisms for relevant retail transactions.
| Solution | Issues documents? | Transmits to myDATA? | Typical fit | Key point |
|---|---|---|---|---|
| Certified provider | Yes | Yes | Businesses needing a managed invoicing process | A recognised channel for the mandatory electronic-invoicing regime. |
| AADE timologio | Yes | Yes, simultaneously | Small businesses with straightforward needs | Free, but not a bookkeeping service. |
| ERP / commercial software | Usually | Yes, when correctly connected | Businesses with broader operational needs | myDATA connectivity alone does not automatically qualify the ERP as an electronic-invoicing channel under the mandatory regime. |
| Special Registration Form | No | Yes | Eligible low-volume businesses | Usage limits apply and it deals only with transmission. |
| Fiscal mechanism | Yes, for relevant retail sales | Yes, as prescribed | Retail activities where required | Specific retail and interconnection rules continue to apply. |
6. What is AADE’s timologio?
timologio is AADE’s free application for issuing digital business documents and transmitting them to myDATA at the same time. A business can configure its profile and organise customers, products and services.
It can be a practical option for a small professional with a modest number of straightforward invoices. It will not necessarily be the best fit for a shop, clinic or business that needs inventory, goods movement, multiple users, complex workflows or dedicated support. Using timologio also does not amount to full accounting or tax compliance management.
7. What is the Special Registration Form?
AADE’s Special Registration Form only transmits data from documents that have already been issued. It is not an invoice-issuing application.
| Bookkeeping system | Official usage limits |
|---|---|
| Double-entry | Up to 50 sales invoices in the previous tax year. |
| Single-entry | Gross revenue of no more than €50,000 or no more than 50 sales invoices in the previous tax year. |
For a single-entry business, access is excluded only when both limits are exceeded: gross revenue above €50,000 and more than 50 sales invoices. Eligibility is assessed using the previous tax year and should be reviewed as the business grows.
8. What happens when I issue an invoice or receipt?
Example A — Service invoice
A consultant issues a €1,000 service invoice plus VAT through an application connected to myDATA. The application creates the legal document, sends the summary and receives a MARK. The consultant must still check the customer, VAT, any withholding, value and document type.
Example B — Retail service receipt
A professional serves a private customer and issues a retail service receipt through the correct lawful channel for that activity. Transmission depends on the applicable arrangement, which may involve a fiscal mechanism, provider, timologio or another permitted solution.
Timing varies by document type, issuing or transmission channel and the applicable rule. The business’s actual setup must therefore be checked before the first document is issued.
9. What happens with expenses?
In ordinary domestic B2B transactions, the supplier generally transmits the data. The customer should monitor incoming expenses, identify missing, incorrect or unknown documents and ensure the required classifications are completed.
myDATA does not decide whether an expense is deductible. Deductibility depends on the real transaction, its business purpose, supporting evidence, payment method and the limitations in Greek tax law. For more detail, see the guide to tax-deductible expenses for sole proprietors in Greece.
10. What does transaction classification mean?
Classification links transmitted data to the correct accounting and tax category. For revenue, it identifies the nature of the income. For expenses, it records the appropriate treatment of the cost and, where required, VAT.
A valid MARK does not prove that the document type, amount, VAT or classification is correct. It confirms a valid transmission, not the correctness of the underlying accounting and tax treatment.
11. How does myDATA connect to VAT and E3?
myDATA data supports pre-filling and cross-checks for tax filings, including VAT returns and the E3 business tax form. Revenue, expenses and classifications should reconcile to the accounting records and the amounts ultimately declared.
A duplicate transmission, missing credit note, incomplete classification or absent supplier document can create discrepancies. Reconciliation should take place before the relevant filing, not only at year-end. myDATA assists reporting and cross-checking but does not replace substantive tax review.
12. myDATA and mandatory electronic invoicing in 2026
myDATA already receives data through several channels. Decisions A.1128/2025 and A.1044/2026 establish a specific mandatory electronic-invoicing regime for the transactions they cover: domestic B2B, B2G and the prescribed wholesale transactions with businesses in non-EU countries.
Under that regime, the electronic invoice must be issued through a certified electronic-invoicing provider or AADE’s timologio application. Emailing a PDF does not automatically create a compliant electronic invoice. Likewise, an ERP’s ability to transmit data to myDATA is not enough where the invoice is not issued through a recognised channel.
| Phase | Businesses covered | Start | Transition |
|---|---|---|---|
| First phase | Gross revenue above €1,000,000 based on the 2023 income-tax return | 2 March 2026 | The conditional transition ended on 3 May 2026. |
| Second phase | All other businesses within scope | 1 October 2026 | Gradual compliance to 31 December 2026 is available only under the conditions of A.1128/2025 and with the prescribed timely declaration using a start date no later than 1 October 2026. |
No later AADE decision changing this timetable was identified in the official related-provisions register. Given the proximity of the second-phase date, businesses should verify their chosen issuing channel and any declaration required to use the conditional transition.
13. Practical comparison for a small business
| Situation | Often practical | What must be checked |
|---|---|---|
| Freelancer issuing a few B2B invoices | timologio or suitable simple software | VAT, withholding, foreign customers and mandatory electronic invoicing. |
| Professional also issuing retail receipts | A solution covering both B2B and B2C properly | Fiscal mechanism, POS interconnection and retail requirements. |
| Business with stock or goods movement | ERP or structured commercial software | Inventory, digital movement documents and support. |
| Business already using an ERP | Retain or upgrade the existing workflow | myDATA connectivity and whether the issuing channel meets the new regime. |
| Business subject to mandatory electronic invoicing | Certified provider or timologio | Start date, transactions in scope, usage declaration and operational readiness. |
There is no universal commercial recommendation. The right setup depends on the activity, transaction volume, retail and wholesale mix, employees, inventory, goods movement and support requirements.
14. Monthly checklist
✓ Have all sales documents been issued?
✓ Were they transmitted successfully?
✓ Is a MARK available where required?
✓ Are supplier invoices shown correctly?
✓ Are any expenses missing?
✓ Are there unknown or incorrect documents?
✓ Have the required classifications been completed?
✓ Does myDATA reconcile to the accounting records?
✓ Have VAT and other filing obligations been checked?
✓ Are the underlying documents retained?
15. Common mistakes
- Confusing invoice issuance with myDATA transmission.
- Confusing myDATA with mandatory electronic invoicing.
- Using an unsuitable channel after the obligation starts.
- Assuming that an emailed PDF automatically qualifies as an electronic invoice.
- Using the wrong document type or classification.
- Transmitting the same document twice through different channels.
- Failing to issue or link a credit note or cancellation.
- Not reviewing supplier documents and expenses.
- Assuming every expense with a MARK is tax-deductible.
- Failing to reconcile before VAT and E3 filings.
- Informing the accountant too late about an issuing error.
16. What should be done immediately after business registration?
- Select the correct issuing method. It should cover the transactions the business will actually make.
- Configure business, service and customer data. Incorrect master data repeats across documents.
- Check VAT, withholding and document types. Different services can require different treatment.
- Run a test document and verify transmission. Check both the issued document and the myDATA result.
- Organise expense documentation. Use a consistent collection and retention process.
- Reconcile regularly with the accountant. Early corrections are usually easier.
If you are still preparing to register, read Starting a Sole Proprietorship in Greece in 2026. The guides on freelancing with an invoice (“blockaki”) and choosing a sole proprietorship or P.C.C. may also be useful.
17. Conclusion
myDATA is more than “uploading invoices”. A correct process starts with lawful issuance, continues with accurate transmission and classification, and ends with reconciliation to the accounting records and tax filings.
The issuing solution should be selected before documents begin — particularly in 2026, when the recognised channel matters for mandatory electronic invoicing. Explore the other tax and financial guides or review the available accounting and tax support.
Frequently asked questions
What is myDATA in simple terms?
AADE’s digital platform for receiving data from a business’s invoices, receipts and accounting entries.
Does every freelancer in Greece need myDATA?
Entities under Article 1 of Law 4308/2014 are generally required to transmit data, subject to statutory exceptions and special cases.
Is AADE’s timologio free?
Yes. It issues digital documents and transmits them to myDATA at the same time.
Do I need accounting software, or can I use timologio?
timologio may cover straightforward issuing needs. The right solution depends on transactions, retail sales, inventory, users and support requirements.
Does the Special Registration Form issue invoices?
No. It only transmits data from documents that have already been legally issued.
Who transmits my supplier invoices?
For ordinary domestic B2B transactions, the supplier generally transmits them. Certain cases require transmission by the customer.
Is an expense automatically deductible if it appears in myDATA?
No. The real transaction, business purpose, evidence, payment and tax limitations must be examined separately.
What is a MARK?
The unique registration number assigned by AADE to each valid myDATA transmission.
Is myDATA the same as electronic invoicing?
No. myDATA concerns data transmission. The 2026 mandatory electronic-invoicing regime requires issuance through the channels specified in the relevant decisions.
What changes on 1 October 2026?
Second-phase businesses enter mandatory electronic invoicing for transactions covered by A.1128/2025. The transition to 31 December 2026 is conditional and not an automatic extension.
Need help with myDATA and invoicing?
Getting the process right from the start reduces errors, discrepancies and corrective work. We review your activity and help you select the appropriate issuing, transmission and accounting workflow.