# BR-KSA-26

Source: https://xmlvalid.com/rules/BR-KSA-26

> If the invoice contains the previous invoice hash (KSA-13), this hash must be base64 encoded SHA256. The hash shall be computed using the following method as described in the ds:transforms block in the XML Invoice Specifications: 1. Remove the <Invoice><ext:UBLExtensions/> block 2. Remove the <Invoice><cac:AdditionalDocumentReference/> block where <cbc:ID/> = QR 3. Remove the <Invoice><cac:Signature/> block 4. Canonicalize the Invoice using the C14N11 standard 5. Hash the resulting string using SHA256 to a binary object 6. Base64 encode the binary object to generate the digest value For the first invoice, the previous invoice hash is "NWZlY2ViNjZmZmM4NmYzOGQ5NTI3ODZjNmQ2OTZjNzljMmRiYzIzOWRkNGU5MWI0NjcyOWQ3M2EyN2ZiNTdlOQ==", the equivalent for base64 encoded SHA256 of "0" (zero) character.

- Level: warning
- Rule sets: ZATCA e-invoicing rules (Saudi Arabia) SDK 3.4.6
- Context: `cac:AdditionalDocumentReference[normalize-space(cbc:ID) = 'PIH']/cac:Attachment`
- Test: `exists(cbc:EmbeddedDocumentBinaryObject) and (cbc:EmbeddedDocumentBinaryObject) != '' and (cbc:EmbeddedDocumentBinaryObject[normalize-space(@mimeCode) = 'text/plain'])`

Validate a document against these rules: https://xmlvalid.com/validate