The issued B2G document is mainly used to cancel invoiced services/products.

json definition with remarks:

{
    "currencyCode": "EUR",
    "invoiceType": "ΤΙΜΟΛΟΓΙΟ ΠΑΡΟΧΗΣ ΥΠΗΡΕΣΙΩΝ",
    "invoiceTypeCode": "5.2",
    "specialInvoiceCategory": 0,
    "variationType": 0,
    "documentTypeCode": "ELB2G",
    "series": "A",
    "number": "585019191",
    "dateIssued": "2023-06-13T23:27:23",
    "OrderCode": "102324", //ΑΡΙΘΜΟΣ ΠΑΡΑΓΓΕΛΙΑΣ
    "B2GDetails": {
        "ContractingAuthorityCode": "1015.E00159.0001",
        "ContractingAuthority": "ΓΕΝΙΚΟ ΝΟΣΟΚΟΜΕΙΟ ΑΤΤΙΚΗΣ Ο ΕΥΑΓΓΕΛΙΣΜΟΣ",
        "ContractTypeCode": "2|2018ΕΠ06600057",
        "ContractReferenceCode": "20SYMV006467658"
    },
    "Issuer": {
        "RegisteredName": "DEMO",
        "ΒrandName": "",
        "Vat": "EL998381010",
        "TaxOffice": "ΦΑΕ ΑΘΗΝΩΝ",
        "Activities": [
            ""
        ],
        "GeneralCommercialRegistryNumber": "001571001000", // ΓΕΜΗ
        "Phones": [
            "2102711067"
        ],
        "faxes": [
            "2102711797"
        ],
        "emails": [
            ",,,,@,,,,,.gr"
        ],
        "Url": "www......gr",
        "Address": {
            "Country": "Ελλάδα",
            "CountryCode": "GR",
            "City": "ΑΘΗΝΑ ",
            "Street": "",
            "Postal": "......"
        }
    },
    "counterParty": {
        "Code": "0115", //ΚΩΔΙΚΟΣ ΠΕΛΑΤΗ
        "registeredName": "ΝΟΣΟΚΟΜΕΙΟ",
        "Vat": "999336270",
        "TaxOffice": "ΛΑΡΙΣΑΣ",
        "Activities": [
            "ΝΟΣΟΚΟΜΕΙΟ"
        ],
        "Phones": [
            "+2410532872"
        ],
        "faxes": [
            "+30 269999999999"
        ],
        "address": {
            "countryCode": "GR",
            "city": "ΛΑΡΙΣΑ",
            "Street": "ΤΣΑΚΑΛΩΦ 1",
            "postal": "41221"
        }
    },
    "Recipient": {
        "ExternalCode": "3516",
        "RegisteredName": "ΔΗΜΟΣ ΑΘΗΝΑΙΩΝ",
        "Vat": "999336270",
        "Address": {
            "CountryCode": "GR",
            "City": "ΑΘΗΝΑ",
            "Street": "Αθηνάς 63, Πλατεία Εθνικής Αντίστασης",
            "Postal": "10552"
        }
    },
    "DistributionDetails": {
        "InternalDocumentId": "1000399998919-5891", // ΥΠΟΧΡΕΩΤΙΚΟ ππεδίο 
        "project": " ΣΥΜΒΑΣΗ 65/2023....", // Συμβολαίου		
        "RelativeDocuments": [
            ""
        ]
    },
    "deliveryOriginDetails": {
        "Address": {
            "City": "ΕΔΡΑ ΤΟΥ",
            "Street": "ΗΡΑΚΛΕΙΟ ΑΤΤ"
        },
        "Phones": [
            "006989999" //
        ]
    },
    "paymentDetails": {
        "previousBalance": "",
        "newBalance": "69120.43",
        "paymentMethods": [
            {
                "paymentMethodTypeCode": 5, // Υποχρεωτικό
                "paymentMethodType": "ΚΑΤΑΘΕΣΗ ΣΕ ΤΡΑΠΕΖΑ", // Υποχρεωτικό
                "amount": 12899.22,
                "remarks": "Επί πίστωση 60 ημερών"
            }
        ]
    },
    "additionalDetails": {
        "accountingDepartmentEmails": [
            ""
        ],
        "transmissionMethod": "A", // "Ε" αν θέλουμε αυτόματα να στέλνεται μνμ στον λήπτη (προσθετουμε το mail στο   πεδίο "accountingDepartmentEmails":)
        "avoidEmailGrouping": false
    },
    "details": [
        {
            "lineNo": 11,
            "classificationLineNo": 1,
            "measurementUnitCodeEN": "H87", // Κωδικος Μονάδας μέτρησης που δηλωνει τεμάχια Yποχρεωτικό !
            "CpvCode": "15511000-3", //Κωδικός CPV αγαθού/ υπηρεσίας/μελέτης/ έργου  βάσει του Κοινού Λεξιλογίου για τις δημόσιες συμβάσεις
            "descriptions": [
                "Madicines for Cancer"
            ],
            "quantity": 1,
            "UnitPrice": 10402.60,
            "netTotal": 10402.60,
            "total": 12899.22,
            "allowancesTotal": 0,
            "vatTotal": 2496.62,
            "vatCategory": "24",
            "vatCategoryCode": 1,
            "recordTypeCode": 0,
            "incomeClassification": {
                "classificationTypeCode": "E3_561_001",
                "classificationCategoryCode": "category1_3"
            }
        }
    ],
    "summaries": {
        "totalNetAmount": 10402.60,
        "totalVATAmount": 2496.62,
        "totalGrossValue": 12899.22
    },
    "vatAnalysis": [
        {
            "name": "24%",
            "vatAmount": 2496.62,
            "underlyingValue": 10402.60
        }
    ],
    "MiscellaneousData": {
        "MoreInformation1": "1. ΕΞΟΦΛΗΣΗ ΤΟΥ ΠΑΡΟΝΤΟΣ.....",
        "MoreInformation2": "8A53C0C50.......",
        "MoreInformation3": ""
    },
    "isDelayedCode": 0
}

Important remarks

• DocumentTypeCode: This filed must be setted to “ELB2G” so that to be declared that the issued document concerns a B2G transaction
  
• Issuer: Τhe details of the issuer are entered in this object and it is mandatory for all the invoices
  
• Counterparty: Τhe details of the counterparty are entered in this object. It is mandatory for the B2G invoices.
  
• Recipient: This field is being used in case that the expenditure concerns a different physical recipient or any department to which the responsibility has been delegated by law. Else the same value with “CounterParty”
  
• InternalDocumentId: It is a unique document number in the issuer’s system
  
• B2GDetails: This field is mandatory for all B2G documents and you find more information in the Features & Modules in B2G invoicing section
  
• PaymethodTypeCode: This code corresponds to the paragraph 8.12 of IAPR myDATA documentation
  
• TransmissionMethod: If this field has value “E”, an email with the invoice url will be sent to the email address that has being setted to the field “AccountingDepartmentEmails”. If it has value “A”, the invoice is only going to be archived.
  
• Details: In this object, each line is a product/service that you sell and all the details of it.
  
• AllowancesCharges: This field is being used for discounts(type = 0) and charges(type=1). This is the way to declare a discount in line level.
  
• MeasurementUnitCodeEN: This field is mandatory for B2G documents and it declares the measurement unit of the product
  
• CpvCode: This field is mandatory for B2G documents and it is a code of good/project/service based on the single classification system for public procurement from the European Union
  
• Summaries: The summary ammounts
  
• VatAnalysis: The analysis of vat amounts by percentage
  
• IsDelayedCode: This field is used for heterochronous transmission. Value 0: Realtime, 1: Problem on the issuer side, 2: Problem on the IAPR side