Can I add documentation to the Account Certification after it’s been submitted?

No – you cannot add attachments or notes to the Account Certification after it’s been submitted.

You can add documentation to a Supplier Invoice (Purchase Orders or Supplier Invoice Requests) at any time. See Attaching Documentation on Supplier Invoices QRG for how to add attachments.  You can also add attachments to Supplier Invoices from the Details for Account Certification report (or any other report that lists the Supplier Invoice) by using the Related Actions button from the Operations Transaction.

You can add notes to some objects in Workday using the Activity Stream functionality.   See the Activity Stream resource for more information.