Creating an invoice assignment rule An invoice assignment rule is used to determine which AP Processor are assigned to a certain invoice. Select AP Administrator > AP Automation Setup > Invoice Assignment Rules. Click Create. Specify this information: Name Specify a name for the new rule. Description Specify a description for the rule. Invoice Assignment Rule Select the custom group that determines the invoices that the invoice assignment rule applies to. See Creating custom groups for AP Invoice Automation. Resource Select the resource to whom the invoice is assigned when the condition is met. Click Save.