This report of final project discussed accounting system of petty cash expenditure on RDWC Paguyangan Sub-district Installation Unit. This research had been completed by obtaining data through library studies, observations, and conducting interviews at RDWC of Paguyangan Sub-district Installation Unit. This writing aimed to determine the system of petty cash expenditure applied by RDWC of Paguyangan Sub-district Installation Unit. Based on the research, it was concluded that the petty cash expenditure on RDWC of Paguyangan Sub-district Installation Unit used a petty cash expenditure document supporting with receipts to make the financial statements well recognized. However, in its implementation, RDWC of Paguyangan Sub-district Installation Unit had not implemented an adequate system according to the Standard Operating Procedure (SOP), as well as a lack of related functions, thus this resulted low activities of the company.