Simplified Procedures in the Processing of Contractor's Billings for Civil Works Paid in the Central Office. Category: Department OrderSub Category: contracts-contractorsSeries: 1991No: 109File: DO_109_S1991.pdfDate: Wednesday, April 10, 1991Tags: Simplified Procedures Processing Contractor's Billings Civil Works Paid Central Office Read more about Simplified Procedures in the Processing of Contractor's Billings for Civil Works Paid in the Central Office.