Note: You should already have the following configuration flags enabled - CFGEnableContractMirroring, CFGEnableInvoiceMirroring
If you notice that when creating an invoice from one of the mirrored contracts and its mirrored invoice is not automatically created, check that the Internal checkbox in the Address entry of the respective W-type companies involved in these mirrored contracts is checked.
If the counterparty on an invoice has Internal selected, the system will automatically create a mirrored invoice.
If the counterparty on an invoice does not have Internal selected, the system will not create a mirrored invoice.
If you have a pair of mirrored contracts involving one W-type company A whose Address entry has Internal un-selected due to business requirements, and one W-type company B with Internal selected, please make sure to create the invoice from company A first if you would like the system to automatically create its mirrored invoice.