A super-luxury villa in Mykonos, with a rental price reaching €5,000 per night, had made sure it was visible wherever it needed to be in order to attract wealthy clients. It appeared on social media, was listed on booking websites and had bank accounts available for payments. There was, however, one place where it remained “invisible”: the Tax Authority’s electronic records.

The thread began with a… tip-off. A citizen filed an identified complaint with the Independent Authority for Public Revenue (AADE) — not simply as general information along the lines of “someone is renting out a villa and not declaring the money.” The complainant provided an address, the websites through which bookings were made and bank account details. In other words, enough pieces of the puzzle for auditors to start looking for the rest. The information was assessed as posing a high tax risk, and the case was referred for an audit. Bank transactions came under scrutiny, and it was eventually revealed that the €5,000-a-night VIP villa had never been registered in the Short-Term Rental Property Registry. The resulting bill for the owner was substantial, with a fine running into tens of thousands of euros.

Hunting down “black” money

The Mykonos case reveals the major change in the way undeclared income in the short-term rental market is now being pursued. The era when a luxury property could be rented behind closed doors and the Tax Authority would practically have to stumble upon it to discover it is over.

Today, every villa, apartment or tourist residence leaves behind a digital trail: listings, photographs, prices, bookings, Property Registration Numbers, payments and, ultimately, tax returns. A complaint may simply be the starting point. Information reaching AADE that is accompanied by specific details is assessed based on tax risk and the ability to cross-check it. An address, a booking link or an IBAN can turn a tip-off into an audit trail. And once auditors begin following that trail, they now have far more sources at their disposal to reconstruct a property’s actual activity.

Cross-checking income declared by property owners against data submitted by Airbnb, Booking.com and Vrbo for the 2020, 2021 and 2022 tax years identified 24,383 unique tax IDs with discrepancies of more than €500. These were individuals who had not registered a business activity under the relevant tourism-accommodation classification code.

The picture becomes even more revealing when broken down by year: 6,222 tax IDs showed discrepancies in 2020, 10,724 in 2021 and 17,525 in 2022. Taxpayers are being asked to correct their returns, while a previous application of a similar procedure for the 2018 and 2019 tax years resulted in 56% voluntary compliance and the declaration of more than €7.2 million in additional income.

The “double storefront”

However, where one loophole is closed, another can emerge. One practice now on the authorities’ radar is what has been dubbed the “double storefront.”

Airbnb or Booking is used to find the customer. There, the prospective guest sees the villa, photographs, pool, location, reviews and price. The transaction, however, may be completed elsewhere.

The prospective customer is moved to direct communication with the owner or manager through a personal website or even social media. The incentive is straightforward: “Book directly and you’ll pay less because there will be no platform commission.” In some cases, the customer may even be asked to cancel a booking that has already been initiated online.

From that point on, the payment may take a different route or be split into several parts. Leaving the platform, of course, does not mean leaving one’s tax obligations behind. Income from a short-term rental must be declared regardless of whether the agreement was concluded through a digital platform or directly.

For AADE, the key question is simple: What was the property’s actual turnover, and how much of it ultimately appeared on the tax return?

To answer that question, different electronic trails can be placed side by side. Every short-term rental property must be registered in the Short-Term Stay Property Registry and receive a Property Registration Number (AMA), which appears on the relevant listings. Stays are declared electronically and the income is reported on the tax return.

This creates an audit chain:

listing → AMA → booking → payment → tax return

Booking data

How the actual turnover can be reconstructed is also illustrated by a case that reached the Dispute Resolution Directorate this year and concerns a company managing bookings for tourist accommodations. The tax years examined were earlier, but the case file provides almost an X-ray of the method used.

Auditors requested booking information from Booking, contracts, property-by-property data and banking records. For the 2019 tax year, against declared booking-management revenue of €58,488, the audit determined revenue of €81,976 — approximately €23,500 more.

Auditors also identified incoming bank transfers totaling €4,106.89 for which, according to the audit, the corresponding tax documents had not been issued.

An even larger pool for audits is created by people operating multiple properties. AADE has identified 1,545 individuals corresponding to a total of 6,344 active AMAs who had income from at least three properties or had acquired a third active AMA from 2024 onward.

Of these, 1,017 had not completed the required registration of business activity, while another 528 had not declared the required classification codes for short-term rentals.

AADE sent them compliance notices and is assessing the results during 2026.