In countries such as Portugal, it is a legal requirement to provide a digital signature for each invoice. This signature verifies that invoice creation sequence and invoice data are not altered after invoice creation. The signature is generated using OpenSSL. This requirement applies to supplier invoices just as it does to customer invoices. For full details of the invoice certification requirement and how the functionality is implemented on the customer side, see Invoice Certification.

In ERS Processor (28.10.13), when you click Process, an invoice is created and a digital signature is then also created. The data used to create the signature is taken from the current invoice, but the signature of the previous invoice is also included. The order of the invoices is determined based on the company, posting year, daybook, and voucher of the invoice. Digital signatures are only created for non-initial invoices.

To view the signature on created invoices, go to Supplier Invoice View (28.1.1.3). Seven grid fields store invoice certification information for each invoice. These grid fields are not visible by default and must be added to the screen.