Revenue Recognition Checklist - Evidence of Arrangement

Is there a signed contract in place? Contract or PO required to recognize revenue. Is there a signed PO in place? Is it normal business practice to accept orders on PO's? If so, then the PO bust state full terms and conditions. Contract or PO required to recognize revenue. Will the current PO be followed up by a system generated PO or a signed contract? If so, then the existing PO is insufficient for revenue recognition.