Translation. Original: offline/korekta-techniczna.md

Technical correction of offline invoice

20.08.2025

Functionality description

Technical correction enables resending an invoice issued in offline mode, which after being sent to the KSeF system was rejected due to technical errors, e.g.:

• non-compliance with the schema,
• exceeding the allowed file size limit,
• invoice duplicate,
• other technical validation errors preventing the assignment of a KSeF number.

Note!

1. Technical correction does not apply to situations related to lack of authorization of entities appearing on the invoice (e.g. self-billing, validation of relations for JST or VAT groups).
2. In this mode, it is not allowed to correct the content of the invoice – technical correction applies only to technical problems preventing its acceptance in the KSeF system.
3. Technical correction can only be sent in an interactive session, but it can apply to offline invoices rejected both in interactive session and in batch session.
4. It is forbidden to technically correct an offline invoice for which another correct correction has already been accepted.

Example flow of technical correction of offline invoice

1. Seller issues an invoice in offline mode.

   • The invoice contains two QR codes:
     • QR Code I – enables invoice verification in the KSeF system,
     • QR Code II – enables confirmation of the issuer's authenticity based on KSeF certificate.

2. Customer receives invoice visualization (e.g. in print form).

   • After scanning QR Code I, the customer receives information that the invoice has not yet been sent to the KSeF system.
   • After scanning QR Code II, the customer receives information about the KSeF certificate, which confirms the issuer's authenticity.

3. Seller sends the offline invoice to the KSeF system.

   • The KSeF system verifies the document.
   • The invoice is rejected due to a technical error (e.g. incorrect compliance with XSD schema).

4. Seller updates their software and generates the invoice again with the same content, but compliant with the schema.

   • Since the XML content differs from the original version, the SHA-256 hash of the invoice file is different.

5. Seller sends the corrected invoice as a technical correction.

   • Specifies in the hashOfCorrectedInvoice field the SHA-256 hash of the original, rejected offline invoice.
   • The offlineMode parameter is set to true.

6. KSeF system correctly accepts the invoice.

   • The document receives a KSeF number.
   • The invoice is linked to the original offline invoice, whose hash was specified in the hashOfCorrectedInvoice field.
   • This enables redirecting the customer from the "old" QR Code I to the corrected invoice.

7. Customer uses QR Code I placed on the original invoice.

   • The KSeF system informs that the original invoice has been technically corrected.
   • The customer receives metadata of the new, correctly processed invoice and has the option to download it from the system.

Sending correction

Correction is sent according to the principles described in the interactive session document, with additional setting:

• offlineMode: true,
• hashOfCorrectedInvoice – hash of the original invoice.

Example in C#: KSeF.Client.Tests.Core\E2E\OnlineSession\OnlineSessionE2ETests.cs

var sendOnlineInvoiceRequest = SendInvoiceOnlineSessionRequestBuilder
    .Create()
    .WithInvoiceHash(invoiceMetadata.HashSHA, invoiceMetadata.FileSize)
    .WithEncryptedDocumentHash(
        encryptedInvoiceMetadata.HashSHA, encryptedInvoiceMetadata.FileSize)
    .WithEncryptedDocumentContent(Convert.ToBase64String(encryptedInvoice))
    .WithOfflineMode(true)
    .WithHashOfCorrectedInvoice(hashOfCorrectedInvoice)    
    .Build();

Example in Java: OnlineSessionController#sendTechnicalCorrection.java

SendInvoiceOnlineSessionRequest sendInvoiceOnlineSessionRequest = new SendInvoiceOnlineSessionRequestBuilder()
           .withInvoiceHash(invoiceMetadata.getHashSHA())
           .withInvoiceSize(invoiceMetadata.getFileSize())
           .withEncryptedInvoiceHash(encryptedInvoiceMetadata.getHashSHA())
           .withEncryptedInvoiceSize(encryptedInvoiceMetadata.getFileSize())
           .withEncryptedInvoiceContent(Base64.getEncoder().encodeToString(encryptedInvoice))
           .withOfflineMode(true)
           .withHashOfCorrectedInvoice(hashOfCorrectedInvoice)
        .build();

Related documents

• Offline modes
• QR codes