Mandatory B2B e-invoicing in Greece from 1 October 2026: what small businesses must do
From 1 October 2026, businesses and freelancers with gross revenue up to €1,000,000 (tax year 2023) must issue B2B invoices only electronically. The transition period, the 12 October filing, provider or timologio, and penalties.
From 1 October 2026, electronic invoicing becomes mandatory for smaller businesses in Greece too: companies, sole proprietors and freelancers that were not part of the first period. Every invoice to a business or to the public sector must be issued only through a certified e-invoicing provider or through the free timologio and myDATAapp applications of AADE, the Greek tax authority. An invoice from a paper invoice book, or from business software without a provider, will be treated as not issued.
The transition period until 31 December 2026 does not apply automatically to everyone. And how you choose to issue invoices affects your costs, your office workload and how you work with your customers. Below is what applies as of 23 September 2026.
Who is in the second period
AADE decision A.1128/2025 split the entities concerned into two groups. Those with gross revenue above €1,000,000 in their income tax return for 2023 have been issuing e-invoices since 2 March 2026. The second period covers all other entities that apply the Greek Accounting Standards (ELP, Law 4308/2014):
- companies (IKE, EPE, AE, OE, EE) with 2023 revenue up to €1,000,000,
- sole proprietors and freelancers who invoice businesses,
- businesses that started after 2023.
The reference year is fixed: if your revenue exceeded €1,000,000 in 2024 or 2025 but not in 2023, you are in the second period.
Which transactions are covered
An electronic invoice is required in three cases:
- Domestic B2B: sales of goods and services to a business that applies the ELP.
- B2B with third countries: to a business outside the European Union, excluding retail.
- B2G: public contracts and other expenses of General Government bodies.
Also covered are purchase documents a business issues when it buys from someone who does not issue invoices, and settlement statements for sales made on behalf of third parties. Retail sales to private individuals do not change, as AADE has stated explicitly, and sales to businesses in other EU member states are not included in the decision.
Transition period and the declaration due by 12 October 2026
From 1 October to 31 December 2026 you may issue e-invoices and, in parallel, keep using your current methods: ERP software that transmits data to myDATA, AADE's digital reporting platform, or handwritten invoices entered in myDATA's special form. The condition is a timely "Declaration of Commencement of Electronic Issuance of Tax Documents", with a start date no later than 1 October 2026.
- With a provider: the provider files the declaration within 10 days of the contract start, and you accept it on the myAADE portal within 10 days (otherwise it is deemed accepted). If the provider does not file, you file it yourself.
- With timologio or myDATAapp: according to AADE's clarification of 22 September 2026, a declaration is needed only if you want to keep the old method as well until the end of the year. You file it yourself by 12 October 2026 on myAADE (Applications > Tax Services > myDATA). If from 1 October you issue exclusively through the apps, you file nothing.
From 1 January 2027, parallel use ends. Under AADE circular E.2004/2026, a handwritten invoice or one from an ERP system without a provider is treated as not issued. The only exception is loss of connection (a power cut or internet outage).
Provider or timologio: how to decide
timologio (on a computer) and myDATAapp (on a phone) are free, need no contract, and AADE explicitly recommends them for small businesses and freelancers. ERP software on its own is not an accepted method: it must run through a provider.
| Criterion | timologio / myDATAapp | Provider |
|---|---|---|
| Cost | Free | Subscription |
| Connection to ERP, POS, inventory | No | Yes |
| Best suited to | Few invoices, simple items | High volume, inventory, several users |
| Commencement declaration | Only for the transition period, filed by you | Always, filed by the provider |
In practice, an engineer with ten invoices a month can easily issue them from timologio. A wholesale business with a warehouse and hundreds of invoices cannot retype every line: it needs a provider connected to its software. You may use more than one provider and use AADE's apps in parallel, which is useful as a backup. Compare the subscription with the hours your staff would lose on manual invoicing. See also our services for business software and myDATA.
When you are the customer: what to check on invoices you receive
Since 2 March 2026, every business has been required to accept B2B and B2G e-invoices. If you have your own provider, you receive them through it. Otherwise, your supplier's provider sends them to you directly, in the way you specify. A provider-issued invoice carries a MARK (the unique registration number in myDATA), an authentication string and a QR code that shows the full document. In timologio, the new version shows the delivery status and lets the recipient reject a document.
From 1 January 2027, a supplier invoice from a paper book or from an ERP system without a provider is, for AADE, not issued. Do not record it without checking: ask for a correct invoice, because it affects how your expense and your VAT are documented. This check is part of regular bookkeeping and accounting.
Penalties
Failure to issue an electronic invoice is treated as failure to issue an invoice (E.2004/2026), and paragraphs 5 and 6 of Article 57 of the Tax Procedure Code (KFD, Law 5104/2024) apply:
| Violation | Single-entry books | Double-entry books |
|---|---|---|
| VAT transactions, first time | 50% of the VAT, at least €250 | 50% of the VAT, at least €500 |
| Repeat violation | 100% of the VAT, at least €500 | 100% of the VAT, at least €1,000 |
| Each further repeat | 200% of the VAT, at least €1,000 | 200% of the VAT, at least €2,000 |
| Transactions without VAT | €500 per audit | €1,000 per audit |
The minimum amounts are calculated cumulatively per tax audit. With dozens of invoices a month, a few weeks of using the wrong method are enough for a noticeable fine.
Incentives for early adoption
Article 71TH of the Greek Income Tax Code (ITC) and decision A.1129/2025 gave a 100% uplift on equipment, software and first-year e-invoicing costs to businesses that switched to exclusive e-invoicing at least two months before the mandatory start. For the second period, that deadline expired in early August 2026. If you made it in time, make sure the costs are recorded correctly in your 2026 books.
What to do before 1 October
- Confirm your period from the gross revenue in your 2023 tax return.
- List your B2B and B2G customers and how many invoices you issue per month.
- Choose your issuing method. With a provider, the contract must start no later than 1 October.
- Decide whether you need the transition period and, if so, check that the declaration is filed by 12 October 2026.
- Run a test: issue a real invoice to a customer you know well and check that it received a MARK and arrived correctly.
- Inform your customers how they will receive invoices.
- Train your staff: who issues, who checks, and what happens if the connection is lost.
If you move goods, Phase B of the Digital Delivery Note also becomes mandatory from 12 October 2026, which is a separate obligation. For background on the framework, see our myDATA guide.
Frequently asked questions
I am a freelancer with only a few invoices. Is timologio enough?
Yes. It is a legal method with no cost and no contract, and if you issue only through timologio or myDATAapp, no declaration is needed.
My ERP already transmits to myDATA. Isn't that enough?
No. Transmitting data to myDATA is not e-invoicing. Your ERP must be connected to a provider; otherwise invoices are treated as not issued from 1 January 2027, or already from 1 October 2026 if there is no declaration.
What happens if I do not file a declaration by 12 October?
You are not covered by the transition period: from 1 October 2026, every B2B or B2G invoice must be issued exclusively in electronic form.
I started my business in 2025. Which period am I in?
The second. Your invoicing channel must be ready before your first B2B invoice.
Sources
- AADE, press release of 22 September 2026 on the timologio and myDATAapp declaration (in Greek)
- AADE, Mandatory electronic invoicing: frequently asked questions
- Decision A.1128/2025, as amended by A.1044/2026 (in Greek)
- AADE, Decision A.1112/2025 on e-invoicing providers (in Greek)
- AADE, Circular E.2004/2026 on e-invoicing penalties (in Greek)
- Tax Procedure Code, Law 5104/2024, Article 57 (in Greek)
Apostolou & Partners helps small businesses and freelancers choose the right way to issue invoices, work out the real cost of each option and move to e-invoicing without disrupting sales. Contact us before 12 October.