Step 3 – Card payment

In this step you issue the same Sales Invoice (1.1) of €12.40 as in step 2, this time paid by card on a POS terminal. In the example the payment provider is Viva.

How it works

A card payment is tied to the invoice through a payment signature that Flexy issues as the provider. The flow has three steps:

1. ERP ── invoice details ──────────▶ Flexy           ⇒ payment signature
2. ERP ── charge + signature ───────▶ Viva (POS)      ⇒ payment id
3. ERP ── invoice + payment id ─────▶ Flexy ──▶ AADE

1. Payment signature. Before charging the card, you ask Flexy for the payment signature of the invoice you are about to issue. The signature contains the invoice UID (derived from VAT number, date, type, series and number), its amounts and the payment amount.
2. Payment. You send the charge to your payment provider (e.g. Viva) together with the signature. Once approved, the provider returns the transaction's payment id (Unique Payment Identity).
3. Invoice. You issue the invoice through Flexy, with card as the payment method and the payment id.

The VAT number, series, aa and date must be the same in the signature and in the invoice. The page puts the same aa and date in both requests; for a new test, reload the page.

1. Issue the payment signature

Save the following as signature.json:

{
  "signature": {
    "provider": "flexy",
    "nsp": "Viva",
    "issuer_vat_number": "<VAT NUMBER>",
    "branch_code": 0,
    "invoice_type": "1.1",
    "invoice_series": "A",
    "invoice_number": "YYYYMMDDHHMMSS",
    "invoice_issued_at": "YYYY-MM-DDTHH:MM:SS+HH:MM",
    "invoice_net_amount": "10.00",
    "invoice_vat_amount": "2.40",
    "invoice_total_amount": "12.40",
    "payment_amount": "12.40",
    "duration": 1,
    "terminal_id": "<TID>"
  }
}

Send it:

curl https://provider-staging.flexy.gr/api/v1/signatures/ \
  -H "Authorization: Bearer <token>" \
  -H "Content-Type: application/json" \
  --data-binary @signature.json

The response (HTTP 201):

{
  "signature": {
    "id": "2f43ec5f-e511-4b2b-b818-9003ecf13f7b",
    "status": "success",
    "uid": "EF50AEE3A2C75459A308044547F252385F5CD83E",
    "nsp_name": "Viva",
    "nsp_value": 1,
    "unsigned_text": "EF50AEE3A2C75459A308044547F252385F5CD83E;;20261004171639;1240;1000;240;1240;<TID>",
    "signed_text": "S2WwpkPyI1rzAc/EelAwVZMeMJIYigB2nMt2/TtdMQwjqbyXWoRu70uy6VsG9d0Bkc9hTFvXFnDkArBLPC15BA==",
    "signature_hex": "4b65b0a643f2235af301cfc47a503055…",
    "timestamp": "20261004171639",
    "expires_at": "2026-10-07T02:16:39.267373Z",
    "seconds_until_expiration": 216000
    // … and the details you sent
  }
}

Give your payment provider the signature details it asks for: usually unsigned_text together with signed_text or signature_hex.

2. Charge the card through your payment provider

Send the €12.40 charge to your terminal through your payment provider (e.g. Viva), together with the signature from step 1, the way the provider defines. Once the customer pays, the provider returns the transaction's payment id.

If the payment is not approved, do not issue the invoice with card as the payment method.

3. Issue the invoice with the payment id

The invoice is the same as in step 2; only the payment method changes. Save the following as invoice.json:

{
  "document": {
    "provider": "flexy",
    "document_type": "invoice",
    "series": "A",
    "aa": "YYYYMMDDHHMMSS",
    "date": "YYYY-MM-DD",
    "provider_details": {
      "document_type": "1.1",
      "payment_methods": [
        { "type": 7, "amount": "12.40", "transaction_id": "<PAYMENT ID>" }
      ]
    },
    "issuer": {
      "legal_name": "Δοκιμαστικός Εκδότης",
      "legal_number": "<VAT NUMBER>",
      "address": {
        "address_line": "Πανεπιστημίου 123",
        "city": "Αθήνα",
        "zip": "10678",
        "country": "GR"
      }
    },
    "counterpart": {
      "legal_name": "Δοκιμαστικός Πελάτης",
      "legal_number": "801434350",
      "address": {
        "address_line": "Σταδίου 456",
        "city": "Θεσσαλονίκη",
        "zip": "54625",
        "country": "GR"
      }
    },
    "items": [
      {
        "title": "Προϊόν δοκιμής",
        "description": "Γραμμή δοκιμής",
        "quantity": "1",
        "unit_measure": "ΤΕΜ",
        "unit_value": "10.00",
        "unit_total": "10.00",
        "taxes": [
          {
            "title": "ΦΠΑ 24%",
            "value_type": "percentage",
            "value": "24.00",
            "tax_sign": "+",
            "on_vat": true,
            "provider_details": { "provider_code": "1" }
          }
        ],
        "provider_details": {
          "classification_category": "category1_1",
          "classification_type": "E3_561_001",
          "vat_classification_category": "1"
        }
      }
    ],
    "totals": {
      "line_extension_amount": "10.00",
      "tax_exclusive_amount": "10.00",
      "tax_amount": "2.40",
      "tax_inclusive_amount": "12.40",
      "payable_amount": "12.40"
    },
    "tax_breakdown": [
      {
        "tax_category_id": "S",
        "tax_rate_percent": "24.00",
        "taxable_amount": "10.00",
        "tax_amount": "2.40"
      }
    ]
  }
}

Send it:

curl https://provider-staging.flexy.gr/api/v1/documents/ \
  -H "Authorization: Bearer <token>" \
  -H "Content-Type: application/json" \
  --data-binary @invoice.json

Once AADE registers the invoice, the API answers with HTTP 201, as in step 2:

{
  "document": {
    "aa": "20261004171639",
    "issue_date": "2026-10-04",
    "provider": "flexy",
    "status": "success",
    "mydata_mark": 400001972099593,
    "mydata_uid": "EF50AEE3A2C75459A308044547F252385F5CD83E",
    "qr_code_url": "https://mydataapidev.aade.gr/TimologioQR/QRInfo?q=…",
    "issuer_vat_number": "<VAT NUMBER>",
    "counterpart_vat_number": "801434350",
    "total_gross_value": "12.40"
    // … and document_data with the whole document, including the payment id
  }
}

Something is wrong

For the errors AADE returns on the invoice see step 2, and for 401 errors step 1.

For ready-to-send requests for every document type see the Examples.