What is the recognized standard for establishing entitlement to financial claims in commercial transactions and service or contracting agreements?

Establishing entitlement to financial claims in commercial transactions and service or contracting agreements relies on the approval of invoices, bearing the signature and stamp of the party obligated to pay, in addition to evidence proving the completion of the agreed-upon work, such as labor timesheets or work handover documents. Invoices that do not bear the stamp or signature of the obligor may not be accepted as independent evidence.