This guide is operational guidance, not tax advice. myDATA requirements can depend on your company, invoice type, accountant workflow, and current AADE rules. Confirm the setup with your accountant before relying on live submissions.

1. Understand what credentials easyTimi needs

For ERP-style myDATA submission, AADE identifies each request with two REST API header values: an AADE user ID and a subscription key. In easyTimi these are stored per company, because each legal issuer should use the credentials that belong to that company.

The AADE API documentation describes these as aade-user-id and ocp-apim-subscription-key. You do not need to paste those header names into easyTimi; you only need the values AADE gives you.

2. Start from the official AADE myDATA area

Open the official AADE myDATA page. In the "myDATA environment" area, AADE links to registration for the myDATA REST API. You will sign in with TAXISnet credentials for the business or authorised user.

If you are testing first, use AADE's development or test process where available. Keep test credentials separate from production credentials so you do not accidentally submit real invoices while validating setup.

3. Register for the myDATA REST API

After signing in, choose the registration form for the myDATA REST API and create a new user registration. Pick a username that uses Latin letters and numbers so it matches AADE's expected format.

When registration succeeds, AADE shows the created username and an API code. The username is the AADE user ID. The API code is the subscription key. Copy both values carefully and store them securely.

4. Add the credentials in easyTimi

Sign in to easyTimi, switch to the Greek company that will issue the invoices, and open Settings. In the Greek myDATA ERP credentials section, enter the AADE user ID and AADE subscription key for that company.

If your account manages multiple companies, repeat this for each Greek company. Do not reuse another company's credentials unless your accountant has explicitly confirmed the authorisation model.

5. Confirm the company and customer data before the first invoice

Before issuing the first invoice, review the seller details, VAT number, country, base currency, invoice numbering, and customer tax information. myDATA submissions are much easier to correct before an invoice has been sent than after a rejected or incorrect submission.

For each line item, use clear descriptions and the right tax treatment. Greek myDATA workflows may also require income classification details such as whether the sale is a service or a good.

6. Create, review, and submit the first invoice

Create the invoice in easyTimi, review the PDF, and check totals before sending. When myDATA is enabled for the company, easyTimi prepares the XML submission, sends it to AADE, and records the returned identifiers such as MARK, UID, and QR URL when AADE accepts the invoice.

If AADE rejects the invoice, read the error message before editing. The most common fixes are missing customer tax details, incorrect invoice classification, invalid VAT treatment, or credentials entered for the wrong company.