Credit note in myDATA after a cancellation: step by step

The guest prepaid three nights for June. The receipt was issued, sent to myDATA and got its MARK. Five days before arrival an email comes in: "Unfortunately we have to cancel." Your policy says free cancellation, so the money goes back.

The money is refunded with one click at your payment provider. The receipt, though, stays in myDATA as income. This article explains what to do with it, step by step.

A document with a MARK cannot be deleted

When myDATA accepts a document, it gives it a MARK (unique registration number). From then on you cannot delete it. There are two official routes:

• Cancellation in myDATA. AADE describes it as "cancelling a document without submitting a new one". The cancellation gets its own MARK and the document counts as cancelled. No new document is issued.
• Credit note. A new document is issued that reverses the original, in full or in part. It has its own numbering and its own MARK.

Which of the two routes fits your case is your accountant's decision. One thing is certain from AADE's documentation, though: documents issued through a certified e-invoicing provider (ΥΠΑΗΕΣ) cannot be cancelled in myDATA (there is a specific error for it, 249). There, the only route is a credit note. See how both are issued from the same place on the myDATA E-Invoicing page.

Which credit note for which document

• Service Receipt (11.2) to a private guest: Retail Credit Note (11.4).
• Service Invoice (2.1) to a company or agency: Correlated Credit Invoice (5.1). In myDATA it carries the MARK of the original invoice, in the correlated documents field.
• There is also 5.2, the Non-Correlated Credit Invoice, for cases not linked to one specific invoice. For a cancelled reservation, it is usually the 5.1.

A detail we learned in practice: the 11.4 does not accept the link to the MARK of the original receipt. If it is sent, myDATA answers with error 205 ("forbidden for this invoice type"). The link to the original receipt is kept in your own system, on the reservation.

Step by step in Bookmatrix.com

1. Cancel the reservation as usual. Cancelling the reservation does not issue a credit note on its own. You handle the document yourself, on purpose.
2. Open the document from the reservation's finance tab and choose "Cancel or credit".
3. See both options side by side: cancel in myDATA, with no new document, or a credit note. For the credit note you see the type (11.4 or 5.1), the series and the next number.
4. Activate the series if it is the first time. Credit note series stay inactive until you need them, and you activate them from the same dialog.
5. Add a reason, optionally, e.g. "cancelled stay". It is printed on the credit note and kept in the history.
6. The credit note is created as a draft, under the original document. The original does not change yet.
7. You issue it from the list. It gets its number, is sent to myDATA and, once it has a MARK, the original shows as "Credited".

The refund itself is a separate step, at your payment provider (Stripe, JCC, epay or another provider) or by bank. The credit note corrects the income. It does not move money.

What to check in myDATA afterwards

• The credit note has a MARK. If not, it was rejected. Read the message, fix it and send it again.
• The 5.1 points to the right original invoice. The MARK in the correlated field must be that of the invoice being reversed.
• The month's totals add up. Receipt and credit note should cancel each other out in income.
• The original was not both cancelled and credited. One route per document, not both.

Three cases that need care

You kept a cancellation fee

If your policy keeps part of the amount, the credit note is not for the full amount, or another document is needed for the cancellation fee. Exactly how, and with what VAT, is your accountant's decision. Talk to them before you issue.

The climate fee document was also issued

The climate resilience fee is charged per day of use. If a special fee document had already been issued for a stay that never happened, check that one with your accountant too, so the monthly fee declaration comes out right.

The property is a short-term rental

There is one more obligation here. According to AADE, if a rental is cancelled and the guest pays under the cancellation policy, an initial "Short-Term Stay Declaration" is due by the 20th of the month after the cancellation.

Invoices to companies after 2 November 2026

From 2 November 2026, invoices to businesses issued by smaller businesses (second period of A.1128/2025, as amended by A.1197/2026) are issued only electronically, through a certified e-invoicing provider or AADE's timologio app. If the original invoice went through a provider, so does its credit note. In Bookmatrix.com this happens on its own: the credit note follows the route of the original.

For how the original receipt is issued in three taps, see this article.

Frequently asked questions

Can I just delete the receipt in my software?

No. Once it has a MARK, it exists in myDATA. Deleting it in your software changes nothing at AADE. You need a cancellation in myDATA or a credit note.

What if the credit note is rejected?

It gets no MARK and stays in the list as not sent, with its number and the error message. You fix the cause and send it again from the list.

I issued a credit note by mistake. What now?

In Bookmatrix.com, if you cancel the credit note, the original document is restored as active. Tell your accountant, though, because this step also shows in myDATA.

Sources

• AADE: myDATA REST API documentation v1.0.12 (document types, error codes, in Greek)
• AADE: Decision A.1128/2025 on mandatory e-invoicing (Gazette B 4937/16.09.2025, in Greek)
• Text of A.1197/2026 (Gazette B 5905/30.09.2026, Taxheaven, in Greek)
• AADE: Short-term rental of property (declaration deadlines, in Greek)
• AADE: FAQ on the climate resilience fee declaration (January 2026, in Greek)

Updated: 14/10/2026. This article is general information, not tax or accounting advice. Your accountant has the final word on your own case.

Want cancellation and credit notes from the same reservation window? Try Bookmatrix.com with a free 14-day demo, or leave your phone number at bookmatrix.com/form and we will call you on the next working day. Or call us at +30 2351 151525.