# Standard Tax Invoice Signature Validation Issue using ZATCA .NET SDK 3.4.6 (Simulation Environment)

**URL:** <https://zatca1.discourse.group/t/standard-tax-invoice-signature-validation-issue-using-zatca-net-sdk-3-4-6-simulation-environment/10516>\
**Category:** Clearance and Reporting\
**Created:** [July 7, 2026, 8:53pm UTC](https://zatca1.discourse.group/t/standard-tax-invoice-signature-validation-issue-using-zatca-net-sdk-3-4-6-simulation-environment/10516 "2026-07-07T20:53:10Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![agentortech](https://dub1.discourse-cdn.com/flex013/user_avatar/zatca1.discourse.group/agentortech/32/1586_2.png) [@agentortech](https://zatca1.discourse.group/u/agentortech)\
**Post date:** [July 7, 2026, 8:53pm UTC](https://zatca1.discourse.group/t/standard-tax-invoice-signature-validation-issue-using-zatca-net-sdk-3-4-6-simulation-environment/10516/1 "2026-07-07T20:53:10Z")

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Dear ZATCA Technical Support Team,

I am integrating **Standard Tax Invoices (B2B)** using the **ZATCA .NET SDK v3.4.6** in the **Simulation Environment**. We are submitting invoices through the **Reporting API** (`POST /e-invoicing/simulation/invoices/reporting/single`) as documented by ZATCA. Our invoice XML is generated according to UBL 2.1, including Header, AdditionalDocumentReference (ICV and PIH only), Supplier, Customer, Delivery, PaymentMeans, TaxTotals, LegalMonetaryTotal and InvoiceLines. The QR element is intentionally not generated manually because it is inserted later by the SDK during the signing process. The certificate (PCSID) and private key were successfully issued by ZATCA, the certificate is stored in Base64 DER format exactly as received from ZATCA, and the private key is stored as Base64(PEM). We sign the invoice using `EInvoiceSigner.SignDocument()` from SDK 3.4.6. During debugging, we confirmed that the invoice hash generated by `GenerateHashMiddleware` is identical to the hash used by `GenerateSignatureMiddleware`; however, after `SignDocument()` completes, regenerating the invoice hash using `EInvoiceHashGenerator` produces a different value. Consequently, `EInvoiceValidator.ValidateEInvoice()` returns the following signature validation errors: **hashedXml** , **invoiceSignedDataDigestValue** , and **signatureValue**. We have thoroughly reviewed our implementation and verified XML generation, tax calculations, legal monetary totals, invoice lines, QR generation, PIH, CSR, certificate parsing, canonicalization, XSL transformation, and hash generation. We also reviewed the SDK internals and observed that after the signature is generated, the SDK executes `TransformXMLResultMiddleware`, which reloads the XML using `LoadXml()`, followed by `FinalizeSignDocumentMiddleware`, which modifies `InnerXml` before returning the signed document. We would appreciate your clarification on whether this behavior is expected in SDK 3.4.6, whether it has been corrected in SDK 3.4.8, whether the invoice hash is expected to change after `SignDocument()` completes, and whether there are any additional requirements for Standard Tax Invoice signing that are not documented. We would also appreciate it if you could confirm the recommended signing sequence for Standard Tax Invoices using the .NET SDK. For reference, we are using the Simulation Reporting API documented by ZATCA: [https://zatcaapidocs.evinciblesolutions.com/reference/post\_invoices-reporting-single](https://zatcaapidocs.evinciblesolutions.com/reference/post_invoices-reporting-single)

“The SDK generates hash A before signing, uses hash A inside SignedInfo, but after SignDocument() the SDK itself regenerates hash B from the returned SignedEInvoice. Could you clarify whether this behavior is expected?”

Thank you for your support.

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**Author:** ![masaftic](https://avatars.discourse-cdn.com/v4/letter/m/87869e/32.png) [@masaftic](https://zatca1.discourse.group/u/masaftic)\
**Post date:** [July 29, 2026, 3:26am UTC](https://zatca1.discourse.group/t/standard-tax-invoice-signature-validation-issue-using-zatca-net-sdk-3-4-6-simulation-environment/10516/2 "2026-07-29T03:26:44Z")

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dear @agentortech

do you have any updates on this matter, i am facing the same issue. local sdk signature validation fails but it is reported without errors or warnings, I am using 3.4.8 sdk version.