Saturday night, 22:10. The day's last guest checks out early for the morning ferry. You issue the receipt, press send, and instead of a MARK you see red: "IssueDate is invalid". The guest is waiting, your accountant is asleep.
myDATA's messages are written for developers. Behind most of them, though, there is a simple cause. Below are five rejections a property runs into often, with their code as AADE's technical documentation gives it, what they mean and what to change.
First: rejected, or just no answer?
Not every red message is a rejection. AADE splits errors into two groups:
- Business errors: myDATA read the document and something fails its checks. It returns a code (e.g. 202) and a description. These are fixed by changing something in the document.
- Technical errors: the call did not complete (e.g. wrong credentials). They have no error code, only an HTTP status.
There is a third case: AADE's service does not answer at that moment. Then the document is not at fault. Wait a little and send it again. In every case, without a MARK the document has not reached AADE. In Bookmatrix.com the myDATA status and message show on every document (see the myDATA E-Invoicing page).
1. HTTP 401: the myDATA credentials do not match
What it says: "Aade-user-id header is missing" or "Access Key does not correspond to given User Id".
Why it happens: the connection to myDATA uses a user name and a key (subscription key) from the myDATA REST API registry. If you created new credentials, if your accountant changed the account, or if one character was copied wrong, every document gets stuck at once.
Fix: log in with TaxisNet to the myDATA REST API registration, look up the current credentials and enter them again in your software. Then resend whatever was left behind.
2. Code 202: Invalid Greek VAT number
What it says: "Invalid Greek VAT number".
Why it happens: on the invoice to a company or travel agency, the customer's VAT number was typed wrong. One swapped digit is enough. Often the number is read out on the phone or copied from an email.
Fix: ask for the VAT number in writing and check it before issuing. In Bookmatrix.com you type the VAT number and the company details come from AADE. If nothing comes back, the number is probably wrong.
3. Codes 204 and 205: field mandatory or forbidden for this type
What it says: "{Field} is mandatory for this invoice type" (204) or "forbidden for this invoice type" (205).
Why it happens: each document type has its own fields. Three examples from accommodation:
- A Service Invoice (2.1) without customer details.
- A 5.1 credit invoice without the MARK of the original invoice.
- An 11.4 retail credit note linked to the MARK of the original receipt. myDATA answers 205, because type 11.4 does not accept that field.
Fix: read which field the message names. Usually the answer is the right document type: a receipt for a private guest, an invoice with VAT number for a business, and the credit note that matches the original.
4. Code 203 (and 207 to 209): totals do not match
What it says: "Gross Value doesn't match with sum of net value plus taxes" (203), or that the sum of the lines does not match the total (207, 208, 209).
Why it happens: a cent went missing somewhere. Usually from a discount applied to the total instead of the line, a final price "rounded" by hand, or VAT calculated on the total instead of per line.
Fix: do not change the total by hand. Change the line (price, discount) and let the software calculate net value, VAT and total. In Bookmatrix.com the amounts come from the reservation's charges, so the fix is made on the charge.
5. Codes 253 and 260: invalid issue date
What it says: "IssueDate is invalid, it must be less or equal than current date".
Why it happens: the document has a date in the future. A classic example: tonight you issue the receipt for the guest who leaves tomorrow, dated tomorrow. Or the reception computer has the wrong date.
Fix: the issue date is the day you issue, not the departure day. Change it to today and send it again.
After the fix
- Send the document again and check that it got a MARK.
- If the document had already been sent to the guest without a MARK, send them the new PDF.
- If the same code repeats across many documents, the problem is in the setup (credentials, series, type), not in each document. Fix it once.
- If you are not sure about the numbering of a rejected document, ask your accountant before resending.
A document issued correctly from the start is not rejected. For how a receipt comes out of the reservation in three taps, see this article.
Frequently asked questions
Where do I find the full list of error codes?
In the myDATA REST API technical documentation that AADE publishes, in the errors section. The link is in the sources below.
A document was rejected. Has it reached AADE?
No. Without a MARK, AADE does not have it. It must be fixed and sent again.
Is it the software or me?
The code tells you. 401 is about connection credentials. 202 and 253 are usually details typed by hand. 203 to 209 and 204/205 can also be a software setting. If they repeat, ask support for help.
Sources
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 to see the myDATA status on every document? 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.