Hi @bilal,
Welcome to our community portal.
please find the answers to your questions below:
Q1. PIH depends on the last generated invoice hash from the solution, if your solution generated invoice with ICV (1,2,3) then PIH of the invoice “3” should be the invoice hash of invoice “2”. Regardless of the submission order as there are no limitation on the submission order, sequence of invoices should be maintained on generation order. Let’s assume that your question was about the generation order, then invoice “2” should have a PIH value set as the hash of credit note1
Note: your solution should assign a new ICV value incrementally with each generated invoice/document.
Q2. PIH depends on the last generated invoice, taking your scenario in consideration, even if the invoice 2 is not submitted due to a connection issue, invoice 3 “PIH” should be the invoice hash of the invoice 2
Q3. ICV should be assigned on generation order not submission order, so the answer would be: ICV should be assigned incrementally on which invoice “was created be the EGS first” not which “was submitted to ZATCA first”
Q4. If the taxpayers is not able to clear their invoices for any failure/disaster reasons either by ZATCA side or taxpayer’s side, they shouldn’t use reporting API to send invoices, instead, they should follow ZATCA’s responding to failure approach, which is specified in the E-invoicing detailed guideline, please refer to the E-invoicing guideline 10th section “failure scenarios” for more information.
Q5. In case that the filed of the invoice type is “1100” in CSR configuration, then you should send all of the 6 documents which are standard & simplified tax invoices and their associated notes. All of the invoices on compliance checks phase will not be recorded as it’s just for testing the taxpayer’s solution capability to generate a valid invoices/notes before sending them to ZATCA through reporting & clearance APIs
**Should you require any further clarifications, please don’t hesitate to reach out, we are more than happy to help 
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