Book keeping plays a vital role in development by providing recorded information which is crucial in the strategic formulation of national development policies and plans. The purpose of the study is to examine the impact of book keeping practices on the financial performance of organizations in Rubaga. Book keeping practices consists of proper accounting records, preparation of accounting records and accounting records procedures, up datedness’ of records whereas financial performance is measured by organizational goal achievement, organizational effectiveness and organizational survival, organizational profitability. A structured questionnaire was used to collect the primary data from 75 mobile money businesses which were selected by means of the random sampling technique. The results revealed that book keeping practices had a significant positive influence on financial performance of mobile money businesses in Rubaga. It was recommended that academic institutions and other bodies which are responsible for organization’s organized training programs for those operators who do not have the technical know-how in the field of accounting to come to grips with it and also provided some mobile money businesses specific accounting guidelines and template forms for capturing accounting practices for the operators to use.