purchase  receipts  for  which  reimbursement  is requested. The  imprest  fund  cashier  prepares  the Standard   Form   1129   in   an   original   and   the number   of   copies   required   by   the   disbursing officer who replenishes the fund. The obligation document  number  of  each  transaction  is  a  re- quired  entry  in  the  Cost  Code  column  of  the Accounting Classification section of the Standard Form 1129. The completed Standard Form 1129, with the original of each paid dealer’s invoice or subvoucher  and  the  original  of  each  DD  Form 1348   (MVO)   attached,   is   submitted   to   the disbursing   officer. The   disbursing   officer reimburses   the   imprest   fund   cashier   for   the amount   of   acceptable   dealers’   invoices   or subvouchers received and furnishes the cashier a paid  copy  of  the  Standard  Form  1129. Refunds From Vendors If  a  vendor  refunds  cash  erroneously  paid before the submission of the Standard Form 1129 covering such payment, the imprest fund cashier must accept the refund, return the money to the imprest fund, and enter the amount of the refund on the original (or copy tendered as the original) of  the  vendor’s  receipt.  If  the  refund  is  made  after submission  of  the  Standard  Form  1129,  the cashier must enter the amount of the refund on his or her retained copy of the form and promptly submit  the  refund  to  the  disbursing  officer. Records Recordskeeping for the imprest fund must be kept  to  a  minimum,  consistent  with  the requirement that adequate controls be maintained. VOUCHER CONTROL.— The imprest fund cashier maintains, in his or her safe, a complete and  orderly  suspense  file  of  all  original  sales documents and Standard Forms 1165 for which the   imprest   fund   cashier   has   not   yet   been reimbursed. When these vouchers are submitted to  the  disbursing  officer  for  reimbursement,  a retained copy of the Standard Form 1129 is filed in the safe pending reimbursement and return of a paid copy of the Standard Form 1129 from the disbursing  officer.  The  paid  copies  of  Standard Forms  1129  returned  by  the  disbursing  officer should  be  filed  in  chronological  order  in  the imprest  fund  cashier’s  safe  and  retained  for  3 years. 5-30 IMPREST FUND PURCHASE LOG.—  An imprest   fund   purchase   log   must   be   locally prepared  and  maintained  by  the  imprest  fund cashier  to  provide  a  record  of  each  transaction. A  recommended  format  of  the  log  is  shown  in figure 5-18. PURCHASE  ORDERS A purchase order is an command  to  buy  certain under specified terms and offer  by  your  ship  or supplies and services conditions  contained in  the  order.  The  purchase  order  is  awarded  as a  result  of  a  quotation.  As  has  been  previously discussed  about  small  purchases,  we  have  gone over  the  most  common  forms  that  are  used  in making  an  open  purchase.  What  will  be  discussed in the following paragraphs is two other types of purchases—the unilateral and bilateral purchase orders. Unilateral Purchase Order A  unilateral  purchase  order,  which  is  most commonly  used,  is  an  offer  by  your  ship  or command to buy certain supplies or services under specific   terms   and   conditions.   The   contractor accepts  the  offer  by  furnishing  the  necessary supplies  or  services  or  by  proceeding  with  the work to where performance has occurred. When you  issue  a  unilateral  purchase  order  the contractor  is  not  legally  obligated  to  perform.  The DD Form 1155 is an offer that the contractor may accept  by  furnishing  the  supplies  or  services  or by  proceeding  with  the  work  to  a  certain  point or  he  can  accept  the  order  simply  by  not furnishing the supplies or providing the services offered. As  the  contracting  officer  you  may,  at  any time before acceptance and by written notice to the  contractor,  withdraw,  amend,  or  cancel  the offer.   The   procedures   for   withdrawal   and cancellation  of  purchase  orders  can  be  found  in the  NAVSUPINST  4200.85. Bilateral  Purchase  Order A bilateral purchase order is an offer by your ship or command that the contractor accepts by signature. The contractor is requested to indicate acceptance of a DD Form 1155 by signing in the Acceptance  block  on  the  face  of  the  form.  The supply   officer, or   whoever   he   or   she   has designated,  will  sign  the  DD  Form  1155  and forward  it  to  the  contractor  for  his  or  her